@Override
  public long estimateMemoryUsageBytes() {
    return 0;
  }
A map from sequential {@code long} keys to {@code long} values backed by a file on disk where the key defines the
offset in the input file.
<p>
During write phase, values are stored in a sliding window of {@link ByteBuffer ByteBuffers} and flushed to disk when
the segment slides out of the window. During read phase, they file is memory-mapped and read.
planetiler-core/src/main/java/com/onthegomap/planetiler/collection/ArrayLongLongMapMmap.java