'Merging multiple XML files is non-trivial and must be done in subclasses.'

def merge(split_files, output_file):

    if (len(split_files) > 1):
        raise NotImplementedError('Merging    multiple    XML    files    is    non-trivial    and    must    be    implemented    for    each    XML    type')
    data.Text.merge(split_files, output_file)
