coerce(other) {
    switch (other.nodeName) {
      case 'ident':
      case 'string':
      case 'literal':
        return new Ident(other.string);
      case 'unit':
        return new Ident(other.toString());
      default:
        return super.coerce(other);
    }
  }
Coerce `other` to an ident.

@param {Node} other
@return {String}
@api public