(self, step)
Called by Loop before training steps, when call_at returned True.
Called by Loop before training steps, when call_at returned True.
Called by Loop before training steps when call_at returned True .
def on_step_begin(self, step):
    """Called by Loop before training steps, when call_at returned True."""
    raise NotImplementedError
def on_step_begin ( self , step ) : raise NotImplementedError