code: def prettify_doc(self, doc):
      punctuation_marks = [".", "!", "?"]
      doc = doc.strip()
      doc += "" if doc[-1:] in punctuation_marks else "."
      return doc
  
imports: import os
  import yaml
  import re
  import doc_gen_snipets
label_desc: Use image node_id 18 for calling the MarkdownFile obj's underlying member method code with example usage: obj.prettify_doc(doc) and returns: doc