parameters: (s, altchars=None)
docstring: Decode a Base64 encoded string.
  
      s is the string to decode.  Optional altchars must be a string of at least
      length 2 (additional characters are ignored) which specifies the
      alternative alphabet used instead of the '+' and '/' characters.
  
      The decoded string is returned.  A TypeError is raised if s were
      incorrectly padded or if there are non-alphabet characters present in the
      string.
docstring_summary: Decode a Base64 encoded string.
docstring_tokens: Decode a Base64 encoded string .
function: def b64decode(s, altchars=None):
      """Decode a Base64 encoded string.
  
      s is the string to decode.  Optional altchars must be a string of at least
      length 2 (additional characters are ignored) which specifies the
      alternative alphabet used instead of the '+' and '/' characters.
  
      The decoded string is returned.  A TypeError is raised if s were
      incorrectly padded or if there are non-alphabet characters present in the
      string.
      """
      if altchars is not None:
          s = _translate(s, {altchars[0]: '+', altchars[1]: '/'})
      try:
          return binascii.a2b_base64(s)
      except binascii.Error, msg:
          # Transform this exception for consistency
          raise TypeError(msg)
function_tokens: def b64decode ( s , altchars = None ) : if altchars is not None : s = _translate ( s , { altchars [ 0 ] : '+' , altchars [ 1 ] : '/' } ) try : return binascii . a2b_base64 ( s ) except binascii . Error , msg : # Transform this exception for consistency raise TypeError ( msg )