code: def add_membership(self, member, role=github.GithubObject.NotSet):
          
          assert isinstance(member, github.NamedUser.NamedUser), member
          assert role is github.GithubObject.NotSet or isinstance(
              role, (str, unicode)), role
          if role is not github.GithubObject.NotSet:
              assert role in ['member', 'maintainer']
              put_parameters = {
                  "role": role,
              }
          else:
              put_parameters = {
                  "role": "member",
              }
          headers, data = self._requester.requestJsonAndCheck(
              "PUT",
              self.url + "/memberships/" + member._identity,
              input=put_parameters
          )
docs: :calls: `PUT /teams/:id/memberships/:user <http://developer.github.com/v3/orgs/teams>`_
          :param member: :class:`github.Nameduser.NamedUser`
          :param role: string
          :rtype: None