constructor(sourceMapConfiguration, options = undefined) {
    super(options);
    this.sourceMapGenerator_ = sourceMapConfiguration.sourceMapGenerator;
    this.lowResolution_ = sourceMapConfiguration.lowResolution;
    this.basepath_ = sourceMapConfiguration.basepath;
    this.outputLineCount_ = 1;
    this.isFirstMapping_ = true;
    this.sourcesInMap_ = new StringSet();
    this.relativeSourceName_ = '';
    this.generated_ = null;
    this.original_ = null;
    this.previousMapping_ = null;
  }
@param {SourceMapGenerator} sourceMapConfiguration
@param {Object} options for ParseTreeWriter