@Nullable
    private PyClass findClassOf(PyExpression argument) {
      PsiElement firstElement = ((PyReferenceExpression)argument).followAssignmentsChain(getResolveContext()).getElement();
      PyClass firstClass = null;
      if (firstElement instanceof PyClass) firstClass = (PyClass)firstElement;
      else if (firstElement instanceof PyExpression) {
        PyType first_type = myTypeEvalContext.getType((PyExpression)firstElement);
        if (first_type instanceof PyClassType) {
          firstClass = ((PyClassType)first_type).getPyClass();
        }
      }
      return firstClass;
    }
@Nullable
    private PyClass findClassOf(PyExpression argument)