def __init__(self, name, host='127.0.0.1', port=27017):
        self.name = name
        self.host = host
        self.port = port
def _acc_grads(g_sum, g_w, g):
  """Accumulate gradients in g, weighted by g_w."""
  return [g_sum_i + g_w * g_i for g_sum_i, g_i in zip(g_sum, g)]