public SnapshotOptions<K, V> setMapper(SnapshotFileMapper mapper) {
    this.mapper = mapper;
    return this;
  }
Overrides the default file mapping for parallel import and export operations.

@param mapper the custom mapper, or null to use the default mapping
@return the snapshot options
@see #setParallelMode(boolean)
geode-core/src/main/java/org/apache/geode/internal/cache/snapshot/SnapshotOptionsImpl.java