code: @Override
    public HColumn<N,V> clear() {
      column.value = null;
      column.timestamp = 0;
      column.ttl = 0;
      column.setTimestampIsSet(false);
      column.setTtlIsSet(false);
      column.setValueIsSet(false);
      return this;
    }
docs: Clear value, timestamp and ttl (the latter two set to '0') leaving only the column name