constructor() {
    super("int")
    this.absoluteValue = 0
  }
A variant of RLEEncoder: rather than storing the actual values passed to
appendValue(), this version stores only the first value, and for all
subsequent values it stores the difference to the previous value. This
encoding is good when values tend to come in sequentially incrementing runs,
because the delta between successive values is 1, and repeated values of 1
are easily compressed with run-length encoding.

Null values are also allowed, as with RLEEncoder.