def get_extension(file_type):
    """
    Returns file extension including '.' according to the given file type
    :param file_type: format of the file such as gzip
    :return: extension of the file such as '.gz'
    """
    if not file_type:
        return ''
    if file_type.lower() == 'gz' or file_type.lower() == 'gzip':
        return '.gz'