code: def p_params(self, p):
          'params : params_begin param_end'
          p[0] = p[1] + (p[2],)
          p.set_lineno(0, p.lineno(1)f p_params(self, p):
          'params : params_begin param_end'
          p[0] = p[1] + (p[2],)
          p.set_lineno(0, p.lineno(1))
docs: params : params_begin param_end