code: public JvmTypeReference wildcardExtends(JvmTypeReference extendsBound) {
  		WildcardTypeReference wildcardTypeReference = typeReferenceOwner.newWildcardTypeReference();
  		wildcardTypeReference.addUpperBound(typeReferenceOwner.toLightweightTypeReference(extendsBound));
  		return wildcardTypeReference.toTypeReference();
  	}
docs: Creates a new wildcard type reference with the given type as the upper bound.
  For example:
  <pre>wildcardExtends(typeRef(CharSequence))</pre>
  would create a type reference representing
  <pre>? extends CharSequence</pre>
  
  @param extendsBound
  the upper bound of the wildcard
  @return the newly created wildcard type reference