'Calculates the sha256 hash of a given string
:example \'85086017559ccc40638fcde2fecaf295e0de7ca51b7517b6aebeaaf75b4d4654\''

@classmethod
def sha256(cls, raw_output=False):

    res = hashlib.sha256(str(random.random()).encode(u'utf-8'))
    if raw_output:
        return res.digest()
    return res.hexdigest()
