def delete_obj_by_address(addr, id)
      @index.remove(id) if @index.is_open?
      header = FlatFileBlobHeader.read(@f, addr, id)
      header.clear_flags
      @space_list.add_space(addr, header.length) if @space_list.is_open?
    end
def delete_obj_by_address(addr, id)
      @index.remove(id) if @index.is_open?
      header = FlatFileBlobHeader.read(@f, addr, id)
      header.clear_flags
      @space_list.add_space(addr, header.length) if @space_list.is_open?
    end
Delete the blob that is stored at the specified address.
 @param addr [Integer] Address of the blob to delete
 @param id [Integer] ID of the blob to delete