def METHOD_NAME(node, key, value, field_name='___pyct_anno'):
  annotations = getattr(node, field_name, {})
  setattr(node, field_name, annotations)
  annotations[key] = value
  # So that the annotations survive gast_to_ast() and ast_to_gast()
  if field_name not in node._fields:
    node._fields += (field_name,)