code: def register_user(self, username, groups=None, policies=None, mount_point=DEFAULT_MOUNT_POINT):
          
          params = {
              'username': username,
              'groups': groups,
              'policies': policies,
          }
          api_path = '/v1/auth/{mount_point}/users/{username}'.format(
              mount_point=mount_point,
              username=username,
          )
          return self._adapter.post(
              url=api_path,
              json=params,
          )
docs: Register a new user and maps a set of policies to it.
  
          Supported methods:
              POST: /auth/{mount_point}/users/{username}. Produces: 204 (empty body)
  
          :param username: Name of the user.
          :type username: str | unicode
          :param groups: List or comma-separated string of groups associated with the user.
          :type groups: list
          :param policies: List or comma-separated string of policies associated with the user.
          :type policies: list
          :param mount_point: The "path" the method/backend was mounted on.
          :type mount_point: str | unicode
          :return: The response of the request.
          :rtype: requests.Response