def sd(series):
    """
    Returns the standard deviation of values in a series.

    Args:
        series (pandas.Series): column to summarize.
    """

    if np.issubdtype(series.dtype, np.number):
        return series.std()
    else:
        return np.nan
def sd ( series ) : if np . issubdtype ( series . dtype , np . number ) : return series . std ( ) else : return np . nan
Returns the standard deviation of values in a series.

    Args:
        series (pandas.Series): column to summarize.