The base implementation of `_.keysIn` which doesn't treat sparse arrays as dense.

@private
@param {Object} object The object to query.
@returns {Array} Returns the array of property names.
function baseKeysIn(object) {
	  if (!isObject$5(object)) {
	    return nativeKeysIn(object);
	  }
	  var isProto = isPrototype(object),
	      result = [];

	  for (var key in object) {
	    if (!(key == 'constructor' && (isProto || !hasOwnProperty$6.call(object, key)))) {
	      result.push(key);
	    }
	  }
	  return result;
	}