6. lgK can be  from 4 to 21.</li>
      <li><code>:hll-type</code> - One of #{4,6,8}, defaults to 8. The HLL_4, HLL_6 and HLL_8  represent different levels of compression of the final HLL array where the  4, 6 and 8 refer to the number of bits each bucket of the HLL array is  compressed down to. The HLL_4 is the most compressed but generally slightly  slower than the other two, especially during union operations.</li>
    </ul>
  </li>
  <li><a href="https://datasketches.apache.org/docs/Theta/ThetaSketchFra