def _fixed_str_size(data):
    """
    Useful for a Pandas column of data that is at its base a string
    datatype. The max length of all records in this column is
    identified and returns a NumPy datatype string, which details a
    fixed length string datatype.
    Py3 NumPy fixed string defaults to wide characters (|U), which is
    unsupported by HDF5.
    """
    str_sz = data.str.len().max()
    return "|S{}".format(str_sz)