My

@org.jetbrains.annotations.Contract(pure = true) 
boolean contains(Object o)

Description copied from interface: java.util.Collection
Returns true if this collection contains the specified element. More formally, returns true if and only if this collection contains at least one element e such that (o==null ? e==null : o.equals(e)).

Overrides:: contains in interface Collection; contains in interface I

Parameters:: o - element whose presence in this collection is to be tested.

Returns:: true if this collection contains the specified element

Throws:: ClassCastException - if the type of the specified element is incompatible with this collection (optional).; NullPointerException - if the specified element is null and this collection does not support null elements (optional).