code: def p_struct(self, p):
          '''struct : STRUCT IDENTIFIER '{' field_seq '}' annotations'''
          p[0] = ast.Struct(
              name=p[2], fields=p[4], annotations=p[6], lineno=p.lineno(2)
          f p_struct(self, p):
          '''struct : STRUCT IDENTIFIER '{' field_seq '}' annotations'''
          p[0] = ast.Struct(
              name=p[2], fields=p[4], annotations=p[6], lineno=p.lineno(2)
          )
docs: struct : STRUCT IDENTIFIER '{' field_seq '}' annotations