fromNode(anchor, base, ignoreClass) {
    var cfi = {
      range: false,
      base: {},
      path: {},
      start: null,
      end: null
    };

    if (typeof base === "string") {
      cfi.base = this.parseComponent(base);
      cfi.spinePos = cfi.base.steps[1].index;
    } else if (typeof base === "object") {
      cfi.base = base;
    }

    cfi.path = this.pathTo(anchor, null, ignoreClass);
    return cfi;
  }
Create a CFI object from a Node
@param {Node} anchor
@param {string | object} base
@param {string} [ignoreClass]
@returns {object} cfi