code: function makeGetJitteredFaces(fr) {
    return function(face, numJitters) {
      if (numJitters && (face.rows !== face.cols)) {
        throw new Error('jittering requires the face to have the same number of rows and cols')
      }
      return [face].concat(!numJitters ? [] : fr.jitterImage(face, numJitters))
    }
  }
docs: /* make sligthly rotated, scaled and mirrored variants of the input image /* can be useful to increase the training set in order to get better results /* but also training time increases with numJitters