code: def get_errors(self):
          
          errors = []
          errors.extend(self._get_signature_errors())
          errors.extend(self._get_additional_errors())
          errors.extend(self._get_entry_errors())
  
          return errors if errors else None
docs: Verify that this MAR file is well formed.
  
          Returns:
              A list of strings describing errors in the MAR file
              None if this MAR file appears well formed.