@Override
  @Nullable
  public PySignature findSignature(@NotNull PyAstFunction function) {
    VirtualFile file = getFile((PyFunction)function);
    if (file != null) {
      return readSignatureAttributeFromFile(file, getFunctionName((PyFunction)function));
    }
    else {
      return null;
    }
  }
@Override
  @Nullable
  public PySignature findSignature(@NotNull PyAstFunction function)