code: function () {
              var filePath = this.getFileName();
              if (!this.__fileContentsCache && filePath) {
                  // Leave the stage early when 'Unknown' is passed
                  // this would otherwise raise an exception when
                  // open_basedir is enabled.
                  if (filePath === "Unknown") {
                      return null;
                  }
  
                  // Return null if the file doesn't actually exist.
                  if (!fs.existsSync(filePath)) {
                      if (process.env.NVM_DIR && process.versions.node) {
                          filePath = path.join(process.env.NVM_DIR, 'src/node-v' + process.versions.node, 'lib', filePath);
                          if (!fs.existsSync(filePath)) {
                              return null;
                          }
                      } else {
                          return null;
                      }
                  }
  
                  this.__fileContentsCache = fs.readFileSync(filePath, 'utf-8');
              }
  
              return this.__fileContentsCache;
          }
docs: Returns the full contents of the file for this frame, if it's known.
  
  @returns {*}