def step_begin(self, step):
    "Callback before training step begins.\n\n    You may use this callback to request evaluation of additional tensors\n    in the graph.\n\n    Args:\n      step: `int`, the current value of the global step.\n\n    Returns:\n      List of `Tensor` objects or string tensor names to be run.\n\n    Raises:\n      ValueError: if we've already begun a step, or `step` < 0, or\n          `step` > `max_steps`.\n    "
    if ((step < 0) or ((self._max_steps is not None) and (step > self._max_steps))):
        raise ValueError(('Invalid step %s.' % step))
    self._current_step = step
    return []
Callback before training step begins.

You may use this callback to request evaluation of additional tensors
in the graph.

Args:
  step: `int`, the current value of the global step.

Returns:
  List of `Tensor` objects or string tensor names to be run.

Raises:
  ValueError: if we've already begun a step, or `step` < 0, or
      `step` > `max_steps`.
def step_begin(self, step):
    "Callback before training step begins.\n\n    You may use this callback to request evaluation of additional tensors\n    in the graph.\n\n    Args:\n      step: `int`, the current value of the global step.\n\n    Returns:\n      List of `Tensor` objects or string tensor names to be run.\n\n    Raises:\n      ValueError: if we've already begun a step, or `step` < 0, or\n          `step` > `max_steps`.\n    "
    if ((step < 0) or ((self._max_steps is not None) and (step > self._max_steps))):
        raise ValueError(('Invalid step %s.' % step))
    self._current_step = step
    return []