diff --git a/python/psi-api/src/com/jetbrains/python/psi/StructuredDocString.java b/python/psi-api/src/com/jetbrains/python/psi/StructuredDocString.java
index eb367d6d0aa7..aec4cebb3e2b 100644
--- a/python/psi-api/src/com/jetbrains/python/psi/StructuredDocString.java
+++ b/python/psi-api/src/com/jetbrains/python/psi/StructuredDocString.java
@@ -77,19 +77,6 @@ public interface StructuredDocString {
   
   // Tags related methods
 
-  @Nullable
-  Substring getTagValue(String... tagNames);
-
-  @Nullable
-  Substring getTagValue(String tagName, @NotNull String argName);
-
-  @Nullable
-  Substring getTagValue(String[] tagNames, @NotNull String argName);
-
-  List<Substring> getTagArguments(String... tagNames);
-
   @Nullable
   Substring getParamByNameAndKind(@NotNull String name, String kind);
-
-  List<String> getAdditionalTags();
 }
diff --git a/python/src/com/jetbrains/python/documentation/DocStringReferenceProvider.java b/python/src/com/jetbrains/python/documentation/DocStringReferenceProvider.java
index 98c467da448e..577534e54a03 100644
--- a/python/src/com/jetbrains/python/documentation/DocStringReferenceProvider.java
+++ b/python/src/com/jetbrains/python/documentation/DocStringReferenceProvider.java
@@ -58,24 +58,25 @@ public class DocStringReferenceProvider extends PsiReferenceProvider {
         final int offset = ranges.get(0).getStartOffset();
         // XXX: It does not work with multielement docstrings
         StructuredDocString docString = DocStringUtil.parse(text);
-        if (docString != null) {
+        if (docString instanceof StructuredDocStringBase) {
+          final StructuredDocStringBase taggedDocString = (StructuredDocStringBase)docString;
           result.addAll(referencesFromNames(expr, offset, docString,
-                                            docString.getTagArguments(StructuredDocStringBase.PARAM_TAGS),
+                                            taggedDocString.getTagArguments(StructuredDocStringBase.PARAM_TAGS),
                                             StructuredDocStringBase.ReferenceType.PARAMETER));
           result.addAll(referencesFromNames(expr, offset, docString,
-                                            docString.getTagArguments(StructuredDocStringBase.PARAM_TYPE_TAGS),
+                                            taggedDocString.getTagArguments(StructuredDocStringBase.PARAM_TYPE_TAGS),
                                             StructuredDocStringBase.ReferenceType.PARAMETER_TYPE));
           result.addAll(referencesFromNames(expr, offset, docString,
                                             docString.getKeywordArgumentSubstrings(), StructuredDocStringBase.ReferenceType.KEYWORD));
 
           result.addAll(referencesFromNames(expr, offset, docString,
-                                            docString.getTagArguments("var"),
+                                            taggedDocString.getTagArguments("var"),
                                             StructuredDocStringBase.ReferenceType.VARIABLE));
           result.addAll(referencesFromNames(expr, offset, docString,
-                                            docString.getTagArguments("cvar"),
+                                            taggedDocString.getTagArguments("cvar"),
                                             StructuredDocStringBase.ReferenceType.CLASS_VARIABLE));
           result.addAll(referencesFromNames(expr, offset, docString,
-                                            docString.getTagArguments("ivar"),
+                                            taggedDocString.getTagArguments("ivar"),
                                             StructuredDocStringBase.ReferenceType.INSTANCE_VARIABLE));
           result.addAll(returnTypes(element, docString, offset));
         }
diff --git a/python/src/com/jetbrains/python/documentation/PyStructuredDocstringFormatter.java b/python/src/com/jetbrains/python/documentation/PyStructuredDocstringFormatter.java
index f74be9bdaf9d..eb1e7c79d875 100644
--- a/python/src/com/jetbrains/python/documentation/PyStructuredDocstringFormatter.java
+++ b/python/src/com/jetbrains/python/documentation/PyStructuredDocstringFormatter.java
@@ -160,19 +160,22 @@ public class PyStructuredDocstringFormatter {
       }
     }
 
-    final List<String> additionalTags = docString.getAdditionalTags();
-    if (!additionalTags.isEmpty()) {
-      result.append("<br/><br/><b>Additional:</b><br/>");
-      result.append("<table>");
-      for (String tagName : additionalTags) {
-        final List<Substring> args = docString.getTagArguments(tagName);
-        for (Substring arg : args) {
-          final String s = arg.toString();
-          result.append("<tr><td align=\"right\"><b>").append(tagName);
-          result.append(" ").append(s).append(":</b>");
-          result.append("</td><td>").append(docString.getTagValue(tagName, s)).append("</td></tr>");
+    if (docString instanceof StructuredDocStringBase) {
+      final StructuredDocStringBase taggedDocString = (StructuredDocStringBase)docString;
+      final List<String> additionalTags = taggedDocString.getAdditionalTags();
+      if (!additionalTags.isEmpty()) {
+        result.append("<br/><br/><b>Additional:</b><br/>");
+        result.append("<table>");
+        for (String tagName : additionalTags) {
+          final List<Substring> args = taggedDocString.getTagArguments(tagName);
+          for (Substring arg : args) {
+            final String s = arg.toString();
+            result.append("<tr><td align=\"right\"><b>").append(tagName);
+            result.append(" ").append(s).append(":</b>");
+            result.append("</td><td>").append(taggedDocString.getTagValue(tagName, s)).append("</td></tr>");
+          }
+          result.append("</table>");
         }
-        result.append("</table>");
       }
     }
     return result.toString();
diff --git a/python/src/com/jetbrains/python/documentation/SectionBasedDocString.java b/python/src/com/jetbrains/python/documentation/SectionBasedDocString.java
index f8c04e753371..1042674b5d32 100644
--- a/python/src/com/jetbrains/python/documentation/SectionBasedDocString.java
+++ b/python/src/com/jetbrains/python/documentation/SectionBasedDocString.java
@@ -365,40 +365,12 @@ public abstract class SectionBasedDocString implements StructuredDocString {
     return null;
   }
 
-  @Nullable
-  @Override
-  public Substring getTagValue(String... tagNames) {
-    return null;
-  }
-
-  @Nullable
-  @Override
-  public Substring getTagValue(String tagName, @NotNull String argName) {
-    return null;
-  }
-
-  @Nullable
-  @Override
-  public Substring getTagValue(String[] tagNames, @NotNull String argName) {
-    return null;
-  }
-
-  @Override
-  public List<Substring> getTagArguments(String... tagNames) {
-    return null;
-  }
-
   @Nullable
   @Override
   public Substring getParamByNameAndKind(@NotNull String name, String kind) {
     return null;
   }
 
-  @Override
-  public List<String> getAdditionalTags() {
-    return null;
-  }
-
   public static class Section {
     private final String myTitle;
     private final List<SectionField> myFields;
@@ -502,10 +474,4 @@ public abstract class SectionBasedDocString implements StructuredDocString {
       return result;
     }
   }
-
-  // MethodsSection
-  // AttributesSection
-  // YieldsSection
-  // RaisesSection
-  // ReturnsSection
 }
diff --git a/python/src/com/jetbrains/python/documentation/StructuredDocStringBase.java b/python/src/com/jetbrains/python/documentation/StructuredDocStringBase.java
index c566639f2772..76cb50c641bc 100644
--- a/python/src/com/jetbrains/python/documentation/StructuredDocStringBase.java
+++ b/python/src/com/jetbrains/python/documentation/StructuredDocStringBase.java
@@ -76,6 +76,8 @@ public abstract class StructuredDocStringBase implements StructuredDocString {
     myDescription = builder.toString();
   }
 
+  public abstract List<String> getAdditionalTags();
+
   @Override
   @NotNull
   public String createParameterType(@NotNull final String name, @NotNull final String type) {
@@ -174,7 +176,6 @@ public abstract class StructuredDocStringBase implements StructuredDocString {
     return result;
   }
 
-  @Override
   @Nullable
   public Substring getTagValue(String... tagNames) {
     for (String tagName : tagNames) {
@@ -186,14 +187,12 @@ public abstract class StructuredDocStringBase implements StructuredDocString {
     return null;
   }
 
-  @Override
   @Nullable
   public Substring getTagValue(String tagName, @NotNull String argName) {
     final Map<Substring, Substring> argValues = myArgTagValues.get(tagName);
     return argValues != null ? argValues.get(new Substring(argName)) : null;
   }
 
-  @Override
   @Nullable
   public Substring getTagValue(String[] tagNames, @NotNull String argName) {
     for (String tagName : tagNames) {
@@ -205,7 +204,6 @@ public abstract class StructuredDocStringBase implements StructuredDocString {
     return null;
   }
 
-  @Override
   public List<Substring> getTagArguments(String... tagNames) {
     for (String tagName : tagNames) {
       final Map<Substring, Substring> map = myArgTagValues.get(tagName);