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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_time_step(self, **create_time_step_kwargs):
 """Creates a time-step and appends it to the list. Args: **create_time_step_kwargs: Forwarded to time_step.TimeStep.create_time_step. """

    ts = time_step.TimeStep.create_time_step(**create_time_step_kwargs)
    assert isinstance(ts, time_step.TimeStep)
    self._time_steps.append(ts)