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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def default_username_algo(email):
 """Generate username for the Django user. :arg str/unicode email: the email address to use to generate a username :returns: str/unicode """

    # bluntly stolen from django-browserid
    # store the username as a base64 encoded sha224 of the email address
    # this protects against data leakage because usernames are often
    # treated as public identifiers (so we can't use the email address).
    username = base64.urlsafe_b64encode(
        hashlib.sha1(force_bytes(email)).digest()
    ).rstrip(b'=')

    return smart_text(username)