code: def client_key_loader(self, f):
          
          @wraps(f)
          def wrapped_f(client_id):
              client_key = f(client_id)
              return {
                  'id': client_id,
                  'key': client_key,
                  'algorithm': current_app.config['HAWK_ALGORITHM']
              }
  
          self._client_key_loader_func = wrapped_f
          return wrapped_f
docs: Registers a function to be called to find a client key.
  
          Function you set has to take a client id and return a client key::
  
              @hawk.client_key_loader
              def get_client_key(client_id):
                  if client_id == 'Alice':
                      return 'werxhqb98rpaxn39848xrunpaw3489ruxnpa98w4rxn'
                  else:
                      raise LookupError()
  
          :param f: The callback for retrieving a client key.