code: def _build(self, *args):
      
      net = args
  
      if not self._layers:
        # If the sequential is passed a single arg, this will end up being
        # wrapped in an extra layer of tuple by *args. Normally we internally
        # handle this in the loop below, but if there are no layers we unpack here
        # in order to make Sequential([]) act like an identity, which seems right.
        if len(args) == 1:
          return args[0]
        else:
          return args
  
      for layer in self._layers:
        if isinstance(net, tuple):
          net = layer(*net)
        else:
          net = layer(net)
  
      return net
docs: Connects the Sequential module into the graph.
  
      Args:
        *args: A tuple of inputs, to be unpacked as the arguments to the first
            layer.
  
      Returns:
        The output value of the last layer.