diff --git a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyClassStub.java b/python/psi-api/src/com/jetbrains/python/psi/stubs/PyClassStub.java
index 5f90dad8e8fe..e4f428cd91c1 100644
--- a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyClassStub.java
+++ b/python/psi-api/src/com/jetbrains/python/psi/stubs/PyClassStub.java
@@ -22,7 +22,6 @@ package com.jetbrains.python.psi.stubs;
 import com.intellij.psi.stubs.NamedStub;
 import com.intellij.psi.util.QualifiedName;
 import com.jetbrains.python.psi.PyClass;
-import com.jetbrains.python.psi.impl.stubs.PyCustomClassStub;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -69,15 +68,12 @@ public interface PyClassStub extends NamedStub<PyClass> {
   }
 
   /**
-   * @param stubClass custom stub class
-   * @param <T>       custom stub class
-   * @return saved stub if it is an instance of passed class or null.
-   * @apiNote This method will be marked as abstract in 2019.2.
-   * @see PyCustomClassStub
-   * @see com.jetbrains.python.psi.impl.stubs.PyCustomClassStubType
+   * @deprecated It is our internal API, try to avoid using it.
+   * It is planned to be removed sooner or later, so please don't rely on this method.
    */
+  @Deprecated
   @Nullable
-  default <T extends PyCustomClassStub> T getCustomStub(@NotNull Class<T> stubClass) {
+  default <T> T getCustomStub(@NotNull Class<T> stubClass) {
     return null;
   }
 }
\ No newline at end of file
diff --git a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyTargetExpressionStub.java b/python/psi-api/src/com/jetbrains/python/psi/stubs/PyTargetExpressionStub.java
index da710a3d44de..fd02413fd30d 100644
--- a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyTargetExpressionStub.java
+++ b/python/psi-api/src/com/jetbrains/python/psi/stubs/PyTargetExpressionStub.java
@@ -18,7 +18,6 @@ package com.jetbrains.python.psi.stubs;
 import com.intellij.psi.stubs.NamedStub;
 import com.intellij.psi.util.QualifiedName;
 import com.jetbrains.python.psi.PyTargetExpression;
-import com.jetbrains.python.psi.impl.stubs.CustomTargetExpressionStub;
 import org.jetbrains.annotations.Nullable;
 
 /**
@@ -58,8 +57,13 @@ public interface PyTargetExpressionStub extends NamedStub<PyTargetExpression>, P
 
   boolean isQualified();
 
+  /**
+   * @deprecated It is our internal API, try to avoid using it.
+   * It is planned to be removed sooner or later, so please don't rely on this method.
+   */
+  @Deprecated
   @Nullable
-  <T extends CustomTargetExpressionStub> T getCustomStub(Class<T> stubClass);
+  <T> T getCustomStub(Class<T> stubClass);
 
   @Nullable
   String getDocString();
diff --git a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStub.java b/python/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStub.java
similarity index 100%
rename from python/psi-api/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStub.java
rename to python/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStub.java
diff --git a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStubType.java b/python/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStubType.java
similarity index 88%
rename from python/psi-api/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStubType.java
rename to python/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStubType.java
index 818b5cd30459..cbfd2afbf45f 100644
--- a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStubType.java
+++ b/python/src/com/jetbrains/python/psi/impl/stubs/CustomTargetExpressionStubType.java
@@ -26,6 +26,11 @@ import com.jetbrains.python.psi.stubs.PyTargetExpressionStub;
 public abstract class CustomTargetExpressionStubType<T extends CustomTargetExpressionStub>
   implements PyCustomStubType<PyTargetExpression, T> {
 
+  /**
+   * @deprecated It is our internal API, try to avoid using it.
+   * It is planned to be removed sooner or later, so please don't rely on this EP.
+   */
+  @Deprecated
   public static final ExtensionPointName<CustomTargetExpressionStubType<? extends CustomTargetExpressionStub>> EP_NAME =
     ExtensionPointName.create("Pythonid.customTargetExpressionStubType");
 
diff --git a/python/src/com/jetbrains/python/psi/impl/stubs/PyClassStubImpl.java b/python/src/com/jetbrains/python/psi/impl/stubs/PyClassStubImpl.java
index 0109bf9e6f4e..327044e09b3b 100644
--- a/python/src/com/jetbrains/python/psi/impl/stubs/PyClassStubImpl.java
+++ b/python/src/com/jetbrains/python/psi/impl/stubs/PyClassStubImpl.java
@@ -140,7 +140,7 @@ public class PyClassStubImpl extends StubBase<PyClass> implements PyClassStub {
 
   @Nullable
   @Override
-  public <T extends PyCustomClassStub> T getCustomStub(@NotNull Class<T> stubClass) {
+  public <T> T getCustomStub(@NotNull Class<T> stubClass) {
     return ObjectUtils.tryCast(myCustomStub, stubClass);
   }
 
diff --git a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStub.java b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStub.java
similarity index 100%
rename from python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStub.java
rename to python/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStub.java
diff --git a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStubType.java b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStubType.java
similarity index 76%
rename from python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStubType.java
rename to python/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStubType.java
index 2dcfee0d5dcb..c7017435e883 100644
--- a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStubType.java
+++ b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomClassStubType.java
@@ -6,6 +6,11 @@ import com.jetbrains.python.psi.PyClass;
 
 public abstract class PyCustomClassStubType<T extends PyCustomClassStub> implements PyCustomStubType<PyClass, T> {
 
+  /**
+   * @deprecated It is our internal API, try to avoid using it.
+   * It is planned to be removed sooner or later, so please don't rely on this EP.
+   */
+  @Deprecated
   public static final ExtensionPointName<PyCustomClassStubType<? extends PyCustomClassStub>> EP_NAME =
     ExtensionPointName.create("Pythonid.customClassStubType");
 }
diff --git a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomStub.java b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomStub.java
similarity index 90%
rename from python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomStub.java
rename to python/src/com/jetbrains/python/psi/impl/stubs/PyCustomStub.java
index f6bf9e83b6e6..5494197fb9e9 100644
--- a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomStub.java
+++ b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomStub.java
@@ -7,7 +7,7 @@ import org.jetbrains.annotations.NotNull;
 
 import java.io.IOException;
 
-public interface PyCustomStub<CustomStubType extends PyCustomStubType> {
+interface PyCustomStub<CustomStubType extends PyCustomStubType> {
 
   /**
    * @return type class to distinguish one custom stub from another.
diff --git a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomStubType.java b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomStubType.java
similarity index 91%
rename from python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomStubType.java
rename to python/src/com/jetbrains/python/psi/impl/stubs/PyCustomStubType.java
index 295851e95d1e..5e38c1250cbb 100644
--- a/python/psi-api/src/com/jetbrains/python/psi/impl/stubs/PyCustomStubType.java
+++ b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomStubType.java
@@ -9,7 +9,7 @@ import org.jetbrains.annotations.Nullable;
 
 import java.io.IOException;
 
-public interface PyCustomStubType<Psi extends PyElement, Stub extends PyCustomStub> {
+interface PyCustomStubType<Psi extends PyElement, Stub extends PyCustomStub> {
 
   /**
    * @param psi element to create stub for
diff --git a/python/psi-api/src/com/jetbrains/python/psi/PyCustomizableStubElementType.java b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomizableStubElementType.java
similarity index 82%
rename from python/psi-api/src/com/jetbrains/python/psi/PyCustomizableStubElementType.java
rename to python/src/com/jetbrains/python/psi/impl/stubs/PyCustomizableStubElementType.java
index a1dccab8b600..9832cc8d903c 100644
--- a/python/psi-api/src/com/jetbrains/python/psi/PyCustomizableStubElementType.java
+++ b/python/src/com/jetbrains/python/psi/impl/stubs/PyCustomizableStubElementType.java
@@ -1,17 +1,16 @@
 // Copyright 2000-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
-package com.jetbrains.python.psi;
+package com.jetbrains.python.psi.impl.stubs;
 
 import com.intellij.psi.stubs.StubInputStream;
 import com.intellij.psi.stubs.StubOutputStream;
-import com.jetbrains.python.psi.impl.stubs.PyCustomStub;
-import com.jetbrains.python.psi.impl.stubs.PyCustomStubType;
+import com.jetbrains.python.psi.PyElement;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
 import java.io.IOException;
 import java.util.List;
 
-public interface PyCustomizableStubElementType<Psi extends PyElement, Stub extends PyCustomStub, StubType extends PyCustomStubType<Psi, ? extends Stub>> {
+interface PyCustomizableStubElementType<Psi extends PyElement, Stub extends PyCustomStub, StubType extends PyCustomStubType<Psi, ? extends Stub>> {
 
   @NotNull
   List<StubType> getExtensions();
diff --git a/python/src/com/jetbrains/python/psi/impl/stubs/PyTargetExpressionStubImpl.java b/python/src/com/jetbrains/python/psi/impl/stubs/PyTargetExpressionStubImpl.java
index 5406b947b178..5feb34aae759 100644
--- a/python/src/com/jetbrains/python/psi/impl/stubs/PyTargetExpressionStubImpl.java
+++ b/python/src/com/jetbrains/python/psi/impl/stubs/PyTargetExpressionStubImpl.java
@@ -17,9 +17,9 @@ package com.jetbrains.python.psi.impl.stubs;
 
 import com.intellij.psi.stubs.StubBase;
 import com.intellij.psi.stubs.StubElement;
+import com.intellij.psi.util.QualifiedName;
 import com.jetbrains.python.PyElementTypes;
 import com.jetbrains.python.psi.PyTargetExpression;
-import com.intellij.psi.util.QualifiedName;
 import com.jetbrains.python.psi.stubs.PyTargetExpressionStub;
 import org.jetbrains.annotations.Nullable;
 
@@ -101,7 +101,7 @@ public class PyTargetExpressionStubImpl extends StubBase<PyTargetExpression> imp
 
   @Nullable
   @Override
-  public <T extends CustomTargetExpressionStub> T getCustomStub(Class<T> stubClass) {
+  public <T> T getCustomStub(Class<T> stubClass) {
     if (stubClass.isInstance(myCustomStub)) {
       return stubClass.cast(myCustomStub);
     }
diff --git a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyDataclassFieldStub.java b/python/src/com/jetbrains/python/psi/stubs/PyDataclassFieldStub.java
similarity index 100%
rename from python/psi-api/src/com/jetbrains/python/psi/stubs/PyDataclassFieldStub.java
rename to python/src/com/jetbrains/python/psi/stubs/PyDataclassFieldStub.java
diff --git a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyDataclassStub.java b/python/src/com/jetbrains/python/psi/stubs/PyDataclassStub.java
similarity index 100%
rename from python/psi-api/src/com/jetbrains/python/psi/stubs/PyDataclassStub.java
rename to python/src/com/jetbrains/python/psi/stubs/PyDataclassStub.java
diff --git a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyNamedTupleStub.java b/python/src/com/jetbrains/python/psi/stubs/PyNamedTupleStub.java
similarity index 100%
rename from python/psi-api/src/com/jetbrains/python/psi/stubs/PyNamedTupleStub.java
rename to python/src/com/jetbrains/python/psi/stubs/PyNamedTupleStub.java
diff --git a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyTypingAliasStub.java b/python/src/com/jetbrains/python/psi/stubs/PyTypingAliasStub.java
similarity index 100%
rename from python/psi-api/src/com/jetbrains/python/psi/stubs/PyTypingAliasStub.java
rename to python/src/com/jetbrains/python/psi/stubs/PyTypingAliasStub.java
diff --git a/python/psi-api/src/com/jetbrains/python/psi/stubs/PyTypingNewTypeStub.java b/python/src/com/jetbrains/python/psi/stubs/PyTypingNewTypeStub.java
similarity index 100%
rename from python/psi-api/src/com/jetbrains/python/psi/stubs/PyTypingNewTypeStub.java
rename to python/src/com/jetbrains/python/psi/stubs/PyTypingNewTypeStub.java