code: function (contentType, contentDisposition) {
          var detected = fileType(this.stream || this.body), // detect the mime from response body
              source = 'forced',
              mime;
  
          // if no overrides provided, we take the values from headers
          !contentDisposition && (contentDisposition = this.headers.one('content-disposition'));
          if (!contentType) {
              contentType = this.headers.one('content-type') && this.headers.one('content-type').value;
              source = HEADER;
          }
  
          // if content type is not found in header, we fall back to the mime type detected
          if (!contentType && detected) {
              contentType = detected.mime;
              source = BODY;
          }
  
          // if still not found, then we use default text
          if (!contentType) {
              contentType = 'text/plain';
              source = 'default';
          }
  
          mime = Response.mimeInfo(contentType, contentDisposition);
          mime.source = source;
          mime.detected = detected && Response.mimeInfo(detected.mime, contentDisposition);
  
          return mime;
      }
docs: @private
  
  @param {String|Header} contentType - override the content-type of the response using this parameter before
  computing the mime  type.
  @param {String|Header} contentDisposition - override the content-disposition of the response before calculating
  mime info.
  
  @returns {Object}
  
  @note example object returned
  {
  source: string // 'header', 'content', 'default' or 'forced'
  type: normalised.type, // sanitised mime type base
  format: normalised.format, // format specific to the type returned
  name: DEFAULT_RESPONSE_FILENAME,
  ext: mimeType.extension(normalised.source) || E, // file extension from sanitised content type
  filename: name + ext,
  // also storing some meta info for possible debugging
  _originalContentType: type, // the user provided mime type
  _sanitisedContentType: normalised.source, // sanitised mime type
  _accuratelyDetected: !normalised.orphan // this being true implies worse case (raw render)
  detected: {} // same as root object, but based on what is detected from content
  }
  @deprecated To be removed in 4.0. Use {@link Response#contentInfo} contentInfo instead.