renderAnnotationElement(annotation) {
    let content = annotation.container.querySelector(".annotationContent");
    if (!content) {
      content = document.createElement("div");
      content.classList.add("annotationContent", this.editorType);
      annotation.container.prepend(content);
    } else if (content.nodeName === "CANVAS") {
      const canvas = content;
      content = document.createElement("div");
      content.classList.add("annotationContent", this.editorType);
      canvas.before(content);
    }

    return content;
  }
Render an annotation in the annotation layer.
@param {Object} annotation
@returns {HTMLElement|null}