'Checks whether the given file format exists in \'methods\'.'

@staticmethod
def _assert_format_exists(file_format, methods):

    try:
        return methods[file_format]
    except KeyError:
        formats = ',    '.join(sorted(methods.keys()))
        raise ValueError(('Unsupported    format:    %r,    try    one    of    %s' % (file_format, formats)))
