def ARGMIN(agg_column,out_column):
  """
  Builtin arg minimum aggregator for groupby

  Example: Get the movie with minimum rating per user.

  >>> sf.groupby("user",
  ...            {'best_movie':tc.aggregate.ARGMIN('rating','movie')})

  """
  return ("__builtin__argmin__",[agg_column,out_column])