code: def validate_contents(file_contents):
      
      for name, contents in file_contents.items():
          if os.path.splitext(name)[1] != '.ipynb':
              continue
          if not contents:
              return False
          try:
              json_object = json.loads(contents)
          except ValueError:
              return False
      return True
docs: Ensures that all ipynb files in FILE_CONTENTS
      are valid JSON files.