code: def proQuestTagToFunc(tag):
      
      if tag in singleLineEntries:
          return lambda x : x[0]
      elif tag in customTags:
          return customTags[tag]
      else:
          return lambda x : x
docs: Takes a tag string, _tag_, and returns the processing function for its data. If their is not a predefined function returns the identity function (`lambda x : x`).
  
      # Parameters
  
      _tag_ : `str`
  
      > The requested tag
  
      # Returns
  
      `function`
  
      > A function to process the tag's data