code: def p_concat(self, p):
          'concat : LBRACE concatlist RBRACE'
          p[0] = Concat(p[2], lineno=p.lineno(1))
          p.set_lineno(0, p.lineno(1)f p_concat(self, p):
          'concat : LBRACE concatlist RBRACE'
          p[0] = Concat(p[2], lineno=p.lineno(1))
          p.set_lineno(0, p.lineno(1))
docs: concat : LBRACE concatlist RBRACE