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 as msg:
  raise TypeError(msg)

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 as msg : raise TypeError ( msg )
decode a base64 encoded string .