code: def construct(self, **bindings):
      
      if hasattr(self._head, 'construct'):
        return self._head.construct(**bindings)
      else:
        raise ValueError(
            'Cannot call construct on a non-template: %s' % type(self._head))
docs: Constructs the graph and returns either a tensor or a sequence.
  
      Note: This method requires that this SequentialLayerBuilder holds a
      template.
  
      Args:
        **bindings: Arguments for every deferred parameter.
      Returns:
        The value that is placed into this.
      Raises:
        ValueError: if this doesn't hold a template.