docs: def delete_index(self, attr):
          """Deletes an index from the Table.  Can be used to drop and rebuild an index,
             or to convert a non-unique index to a unique index, or vice versa.
             @param attr: name of an indexed attribute
             @type attr: string
          """
          if attr in self._indexes:
              del self._indexes[attr]
              self._uniqueIndexes = [ind for ind in self._indexes.values() if ind.is_unique]
          return self