code: def b64encode(s, altchars=None):
      
      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)
docs: 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.