in src/ppxgboost/PPBooster.py [0:0]
def hmac_msg(prf_key_hash, feature):
"""
Using hmac to produce the pseudonyms for the feature vector.
:param prf_key_hash: hash key as bytes
:param feature: feature name as a string (encoded using 'UTF-8')
:return: hmac value
"""
message = bytes(feature, encodings.utf_8.getregentry().name)
sig = base64.b64encode(hmac.new(prf_key_hash, message, hashlib.sha256).digest())
return sig.decode()