mixed bag vs multiformity

mixed bag

noun
  • Something tending to have both good and bad results or characteristics; something having a mixture of advantages and disadvantages. 

  • Any bag containing a mixture of something. 

  • A group of entities with few characteristics in common. 

multiformity

noun
  • The quality of being multiform, or having many forms. 

How often have the words mixed bag and multiformity occurred in a corpus of books? (source: Google Ngram Viewer )