<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _as_graph_element(self):
 """Returns the underlying graph element if possible."""

    if self.is_sequence():
      raise TypeError('A Pretty Tensor that holds a sequence cannot be '
                      'represented as a graph element.')
    else:
      # Self might be holding something else that isn't a true tensor, so
      # if the 'tensor' can behave like a graph element, look for its
      # _AsGraphElement method and call it. Graph elements themselves may not
      # have or need this method, so just return other items directly.
      obj = self.tensor
      conv_fn = getattr(obj, '_as_graph_element', None)
      if conv_fn and isinstance(conv_fn, collections.Callable):
        obj = conv_fn()
      return obj