docs: def p_primary_expr_no_brace_4(self, p):
          """primary_expr_no_brace : LPAREN expr RPAREN"""
          if isinstance(p[2], self.asttypes.GroupingOp):
              # this reduces the grouping operator to one.
              p[0] = p[2]
          else:
              p[0] = self.asttypes.GroupingOp(expr=p[2])
              p[0].setpos(p)