code: func NewBlockFilter(backend Backend, block common.Hash, addresses []common.Address, topics [][]common.Hash) *Filter {
  	// Create a generic filter and convert it into a block filter
  	filter := newFilter(backend, addresses, topics)
  	filter.block = block
  	return filter
  }
docs: // NewBlockFilter creates a new filter which directly inspects the contents of
  // a block to figure out whether it is interesting or not.