code: function isValidSelector(value) {
      "use strict";
      if (isString(value)) {
          try {
              // phantomjs env has a working document object, let's use it
              document.querySelector(value);
          } catch(e) {
              if ('name' in e && (e.name === 'SYNTAX_ERR' || e.name === 'SyntaxError')) {
                  return false;
              }
          }
          return true;
      } else if (isObject(value)) {
          if (!value.hasOwnProperty('type')) {
              return false;
          }
          if (!value.hasOwnProperty('path')) {
              return false;
          }
          if (['css', 'xpath'].indexOf(value.type) === -1) {
              return false;
          }
          return true;
      }
      return false;
  }
docs: Checks if value is a valid selector Object.
  
  @param  mixed  value
  @return Boolean