static fromSourceMap(aSourceMapConsumer) {
    const sourceRoot = aSourceMapConsumer.sourceRoot
    const generator = new SourceMapGenerator({
      file: aSourceMapConsumer.file,
      sourceRoot,
    })
    aSourceMapConsumer.eachMapping(function (mapping) {
      const newMapping = {
        generated: {
          line: mapping.generatedLine,
          column: mapping.generatedColumn,
        },
      }

      if (mapping.source != null) {
        newMapping.source = mapping.source
        if (sourceRoot != null) {
          newMapping.source = util.relative(sourceRoot, newMapping.source)
        }

        newMapping.original = {
          line: mapping.originalLine,
          column: mapping.originalColumn,
        }

        if (mapping.name != null) {
          newMapping.name = mapping.name
        }
      }

      generator.addMapping(newMapping)
    })
    aSourceMapConsumer.sources.forEach(function (sourceFile) {
      let sourceRelative = sourceFile
      if (sourceRoot !== null) {
        sourceRelative = util.relative(sourceRoot, sourceFile)
      }

      if (!generator._sources.has(sourceRelative)) {
        generator._sources.add(sourceRelative)
      }

      const content = aSourceMapConsumer.sourceContentFor(sourceFile)
      if (content != null) {
        generator.setSourceContent(sourceFile, content)
      }
    })
    return generator
  }
Creates a new SourceMapGenerator based on a SourceMapConsumer

@param aSourceMapConsumer The SourceMap.