import hashlib


def digest_id(wordage):
    """
    return a deterministic digest of input
    the 'b' is an experiment forcing the first char to be non numeric
    but valid hex; which is in no way required for RDF
    but may help when using the identifier in other contexts
    which do not allow identifiers to begin with a digit

    :param wordage  the string to hash
    :returns 20 hex char digest
    """
    return 'b' + hashlib.sha1(wordage.encode('utf-8')).hexdigest()[1:20]