function baseKeys(object) {
  if (!isPrototype(object)) {
    return nativeKeys(object);
  }
  var result = [];
  for (var key in Object(object)) {
    if (hasOwnProperty.call(object, key) && key != 'constructor') {
      result.push(key);
    }
  }
  return result;
}
The base implementation of `_.keys` which doesn't treat sparse arrays as dense.

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