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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 b64encode(s, altchars=None):
 """Encode bytes using the standard Base64 alphabet. Argument ``s`` is a :term:`bytes-like object` to encode. Optional ``altchars`` must be a byte string of length 2 which specifies an alternative alphabet for the '+' and '/' characters. This allows an application to e.g. generate url or filesystem safe Base64 strings. The result is returned as a :class:`bytes` object. """

    if altchars is not None:
        altchars = _get_bytes(altchars)
        assert len(altchars) == 2, repr(altchars)
    if version_info < (3, 0):
        if isinstance(s, text_type):
            raise TypeError('a bytes-like object is required, not \''
                            + type(s).__name__ + '\'')
    return builtin_encode(s, altchars)