code: def remove_empty_tags(self, tags=None):
          
          new_tags = {}
          old_tags = tags if tags else self.get("tags")
          for tag in old_tags.keys():
              if old_tags[tag] is not None:
                  new_tags[tag] = old_tags[tag]
          if not tags:
              self._requirements["tags"] = new_tags
              return None
          return new_tags
docs: Tags whose value is set to None shall be removed from tags.
          :param tags: Tags which are to be processed.
          If None, tags found in self._requirements are used.
          :return: If tags is not None, returns dict with processed tags. Else returns None.