docs: def get_parent(self, tree, alt=None):
          """
          Get parent for given `tree` or `alt` if not found.
  
          Args:
              tree (obj): :class:`.Tree` instance, which is already stored in DB.
              alt (obj, default None): Alternative value returned when `tree` is
                  not found.
  
          Returns:
              obj: :class:`.Tree` parent to given `tree`.
          """
          parent = self.parent_db.get(tree.path)
  
          if not parent:
              return alt
  
          return list(parent)[0]