def first(series, order_by=None):
    """
    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.
    """

    if order_by is not None:
        series = order_series_by(series, order_by)
    first_s = series.iloc[0]
    return first_s
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.