code: def first(series, order_by=None):
      
  
      if order_by is not None:
          series = order_series_by(series, order_by)
      first_s = series.iloc[0]
      return first_s
docs: Returns the first value of a series.
  
      Args:
          series (pandas.Series): column to summarize.
  
      Kwargs:
          order_by: a pandas.Series or list of series (can be symbolic) to order
              the input series by before summarization.