def each(&block)
      @btree.each do |index, entry|
        if entry.is_a?(Collisions)
          break unless entry.each do |c_entry|
            yield(c_entry.key, c_entry.value)
          end
        else
          yield(entry.key, entry.value)
        end
      end
    end
def each(&block)
      @btree.each do |index, entry|
        if entry.is_a?(Collisions)
          break unless entry.each do |c_entry|
            yield(c_entry.key, c_entry.value)
          end
        else
          yield(entry.key, entry.value)
        end
      end
    end
Calls the given block for each key/value pair.
 @yield(key, value)