code: function create(content, url) {
    url = url || '<source>';
    const map = new SourceMapGenerator({ file: url });
    const lines = content.split('\n');
  
    for (let l = 1, n = lines.length; l <= n; l++) {
      // Skip empty
      if (lines[l - 1]) {
        map.addMapping({
          source: url,
          original: { line: l, column: 0 },
          generated: { line: l, column: 0 }
        });
      }
    }
  
    map.setSourceContent(url, content);
    return map;
  }
docs: Create source map from 'content'
  @param {String} content
  @param {String} [url]
  @returns {SourceMapGenerator}