new_contents: '''
  Utilities to search files and retain meta data about files.
  '''
  import logging
  import os
  import mmap
  
  
  def map_file(path=None):
      logging.debug("map_file: " + path)
  
      file_map = ""
  
      if path is None or path is os.path.isfile(path):
          logging.error('generate string is None')
          logging.error('path is not a path.')
      else:
          with open(path) as infile:
              file_map = mmap.mmap(infile, 0, access=mmap.ACCESS_READ)
  
      return file_map
  
  
  def mask_mmap(file_map=None, mask_model=None):
      logging.debug("file_map: " + file_map)
  
      masked_line = ""
  
      if file_map is None:
          logging.error("file_map is None")
      else:
          for line in iter(file_map.readline, ""):
              masked_line = mask_line(line, mask_model)
  
  
  
  def mask_line(line=None, mask_model=None):
      logging.debug("mask_line processing.")
  
      new_line = ""
  
      if line is None or line is mask_model:
          logging.error("line and or mask_model is None")
      else:
          for mask in mask_model:
              print(mask)
  
  
      return new_line
  
  
subject: Write three functions to begin the feature to mask values of some keyvalue pairs. Publish to begin writing the tests and making these work and process better. Write it through.