@Nullable
  private static PyExpression getValue(@Nullable PyStatement def) {
    if (def == null) return null;
    if (def instanceof PyAssignmentStatement) {
      return ((PyAssignmentStatement)def).getAssignedValue();
    }
    return ((PyAugAssignmentStatement)def).getValue();
  }
@Nullable
  private static PyExpression getValue(@Nullable PyStatement def)