code: def add_member(self, username, permissions, api=None):
          
          api = api or self._API
          data = {
              'username': username,
              'permissions': permissions
          }
  
          response = api.post(
              url=self._URL['members'].format(id=self.id),
              data=data
          )
          data = response.json()
          return Member(api=api, **data)
docs: Add member to a dataset
          :param username: Member username
          :param permissions: Permissions dict
          :param api: Api instance
          :return: New member instance