docs: def Query(cls, index_urn, target_prefix="", limit=100, token=None):
      """Search the index for matches starting with target_prefix.
  
      Args:
         index_urn: The index to use. Should be a urn that points to the sha256
           namespace.
         target_prefix: The prefix to match against the index.
         limit: Either a tuple of (start, limit) or a maximum number of results to
           return.
         token: A DB token.
  
      Returns:
        URNs of files which have the same data as this file - as read from the
        index.
      """
      return data_store.DB.FileHashIndexQuery(
          index_urn, target_prefix, limit=limit)