code: def lookupEncoding(encoding):
      
      if isinstance(encoding, binary_type):
          try:
              encoding = encoding.decode("ascii")
          except UnicodeDecodeError:
              return None
  
      if encoding is not None:
          try:
              return webencodings.lookup(encoding)
          except AttributeError:
              return None
      else:
          return None
docs: Return the python codec name corresponding to an encoding or None if the
      string doesn't correspond to a valid encoding.