function wrapperChain() {
      return chain(this);
    }
Enables explicit method chaining on the wrapper object.

@name chain
@memberOf _
@category Chain
@returns {*} Returns the `lodash` object.
@example

var users = [
  { 'user': 'barney', 'age': 36 },
  { 'user': 'fred',   'age': 40 }
];

// without explicit chaining
_(users).first();
// => { 'user': 'barney', 'age': 36 }

// with explicit chaining
_(users).chain()
  .first()
  .pick('age')
  .value();
// => { 'age': 36 }