docs: public boolean containsKey(final Object key)
      {
          @DoNotSub final int mask = values.length - 1;
          @DoNotSub int index = Hashing.hash(key, mask);
  
          boolean found = false;
          while (missingValue != values[index])
          {
              if (key.equals(keys[index]))
              {
                  found = true;
                  break;
              }
  
              index = ++index & mask;
          }
  
          return found;
      }