code: public static SanitizedContent filterImageDataUri(SoyValue value) {
      value = normalizeNull(value);
      return filterImageDataUri(value.coerceToString());
    }
docs: Makes sure that the given input is a data URI corresponding to an image.
  
  <p>SanitizedContent kind does not apply -- the directive is also used to ensure no foreign
  resources are loaded.