class_docstr: Removes all dirty characters (non English alphabet) from tokens and converts words to
  lower case. Need to tokenize first.
  Original tokens will be replaced by normalized tokens.
  
  >>> normalizer = Normalizer()
  creating: createNormalizer
code: def __init__(self, bigdl_type="float"):
      super(Normalizer, self).__init__(bigdl_type)
  
imports: import sys
  import six
  from bigdl.dllib.feature.common import Preprocessing
  from bigdl.dllib.feature.text import TextFeature
  from bigdl.dllib.utils.file_utils import callZooFunc
  from bigdl.dllib.utils.log4Error import *
label_desc: Use image node_id 1 to create a new Normalizer object from inherited base classes: TextTransformer with example: obj = Normalizer(bigdl_type)