code: function isDataSource( image ) {
  
      const source = (typeof image === "string" ? image : image.src).substr(0, 5);
  
      // base 64 string contains data-attribute, the MIME type and then the content, e.g. :
      // e.g. "data:image/png;base64," for a typical PNG, Blob string contains no MIME, e.g.:
      // blob:http://localhost:9001/46cc7e56-cf2a-7540-b515-1d99dfcb2ad6
      return source === "data:" || source === "blob:";
  }
docs: checks whether the contents of an Image are either a base64 encoded string
  or a Blob
  
  @private
  @param {Image|string} image when string, it is the src attribute of an Image
  @return {boolean}