code: def _validate_timestep(self, timestep):
      assert_is_type(timestep, "AUTO", "duration", "number_of_trees")
      if timestep == "AUTO":
          timestep = "number_of_trees"
      return timestep
  
file_path: h2o-3/h2o-py/h2o/model/extensions/scoring_history.py
imports: from h2o.exceptions import H2OValueError
  from h2o.plot import decorate_plot_result, get_matplotlib_pyplot, RAISE_ON_FIGURE_ACCESS
  from h2o.utils.shared_utils import can_use_pandas
  from h2o.utils.typechecks import assert_is_type
label_desc: Use image node_id 1 for calling the ScoringHistoryTrees obj's underlying member method code with example usage: obj._validate_timestep(timestep) and returns: timestep