function baseKeysIn(object) {
      object = object == null ? object : Object(object);

      var result = [];
      for (var key in object) {
        result.push(key);
      }
      return result;
    }
The base implementation of `_.keysIn` which doesn't skip the constructor
property of prototypes or treat sparse arrays as dense.

@private
@param {Object} object The object to query.
@returns {Array} Returns the array of property names.