docs: def add(self, anchor):
          """Add a new anchor to the repository.
  
          This will create a new ID for the anchor and provision new storage for
          it.
  
          Returns: The storage ID for the Anchor which can be used to retrieve
              the anchor later.
  
          """
          anchor_id = uuid.uuid4().hex
          anchor_path = self._anchor_path(anchor_id)
          with anchor_path.open(mode='wt') as f:
              save_anchor(f, anchor, self.root)
  
          return anchor_id