code: function (content, properties) {
      var lines = content.split(lineEndingRE);
      lines = replaceProperties(lines, properties);
      lines = replaceSymbols(lines);
      return lines.join('\n');
    }
docs: Given some text, we find all references that correlate with provided properties
  and replace them with the value assigned to the property.
  
  @param {!string} content
  @param {!Object} properties
  @returns {!string}