First ones I noticed were codecs.encode() and codecs.decode(). Here is a list of other candidates, although they are not all documented, so maybe should not all be in __all__.

>>> import codecs
>>> public = (a for a in dir(codecs) if not a.startswith("_"))
>>> sorted(set(public).difference(codecs.__all__))
['BufferedIncrementalDecoder', 'BufferedIncrementalEncoder', 'Codec', 'CodecInfo', 'IncrementalDecoder', 'IncrementalEncoder', 'StreamReader', 'StreamReaderWriter', 'StreamRecoder', 'StreamWriter', 'ascii_decode', 'ascii_encode', 'backslashreplace_errors', 'builtins', 'charmap_build', 'charmap_decode', 'charmap_encode', 'decode', 'encode', 'escape_decode', 'escape_encode', 'getdecoder', 'getencoder', 'getincrementaldecoder', 'getincrementalencoder', 'getreader', 'getwriter', 'iterdecode', 'iterencode', 'latin_1_decode', 'latin_1_encode', 'make_encoding_map', 'make_identity_dict', 'raw_unicode_escape_decode', 'raw_unicode_escape_encode', 'readbuffer_encode', 'sys', 'unicode_escape_decode', 'unicode_escape_encode', 'unicode_internal_decode', 'unicode_internal_encode', 'utf_16_be_decode', 'utf_16_be_encode', 'utf_16_decode', 'utf_16_encode', 'utf_16_ex_decode', 'utf_16_le_decode', 'utf_16_le_encode', 'utf_32_be_decode', 'utf_32_be_encode', 'utf_32_decode', 'utf_32_encode', 'utf_32_ex_decode', 'utf_32_le_decode', 'utf_32_le_encode', 'utf_7_decode', 'utf_7_encode', 'utf_8_decode', 'utf_8_encode']