code: def b64encode(s, altchars=None):
      
      # Strip off the trailing newline
      encoded = binascii.b2a_base64(s)[:-1]
      if altchars is not None:
          return encoded.translate(string.maketrans(b'+/', altchars[:2]))
      return encoded
docs: Encode a string using Base64.
  
      s is the string to encode.  Optional altchars must be a string of at least
      length 2 (additional characters are ignored) which specifies an
      alternative alphabet for the '+' and '/' characters.  This allows an
      application to e.g. generate url or filesystem safe Base64 strings.
  
      The encoded string is returned.