The length of the largest magic string + its offset

def _max_lengths():
    """ The length of the largest magic string + its offset"""
    max_header_length = max([len(x.byte_match) + x.offset
                             for x in magic_header_array])
    max_footer_length = max([len(x.byte_match) + abs(x.offset)
                             for x in magic_footer_array])
    return max_header_length, max_footer_length