function invert(object, multiValue, guard) {
      if (guard && isIterateeCall(object, multiValue, guard)) {
        multiValue = undefined;
      }
      var index = -1,
          props = keys(object),
          length = props.length,
          result = {};

      while (++index < length) {
        var key = props[index],
            value = object[key];

        if (multiValue) {
          if (hasOwnProperty.call(result, value)) {
            result[value].push(key);
          } else {
            result[value] = [key];
          }
        }
        else {
          result[value] = key;
        }
      }
      return result;
    }
Creates an array of the own enumerable property names of `object`.

**Note:** Non-object values are coerced to objects. See the
[ES spec](http://ecma-international.org/ecma-262/6.0/#sec-object.keys)
for more details.

@static
@memberOf _
@category Object
@param {Object} object The object to query.
@returns {Array} Returns the array of property names.
@example

function Foo() {
  this.a = 1;
  this.b = 2;
}

Foo.prototype.c = 3;

_.keys(new Foo);
// => ['a', 'b'] (iteration order is not guaranteed)

_.keys('hi');
// => ['0', '1']