code: def p_ex_map_pair(self, p):
          
          try:
              p[0] = {p[1]: p[3]}
          except TypeError:
              msg = u"%s is an invalid hash key because it cannot be hashed." % repr(p[1])
              self.errors.append((msg, p.lineno(2), self.path))
              p[0] = {}
docs: ex_map_pair : ex_map_elem COLON ex_map_elem