public function into(Map $target)
    {
        $this->walk(function ($value, $key) use ($target) {
            $target->set($key, $value);
        });
        return $target;
    }
public function into(Map $target)
    {
        $this->walk(function ($value, $key) use ($target) {
            $target->set($key, $value);
        });
        return $target;
    }
public function into ( Map $ target ) { $ this -> walk ( function ( $ value , $ key ) use ( $ target ) { $ target -> set ( $ key , $ value ) ; } ) ; return $ target ; }
Put all of this map's elements into the target and return the target.

```
$words = new MapOfStrings([ 'foo', 'bar' ]);
$words->map('strlen($_0)')->into(new MapOfInts)->sum(); // 6
```

Use when you've mapped your elements into a different type, and you
want to fluently perform operations on the new type. In the example,
the sum of the words' lengths was calculated.

@return $target
@api
Put all of this map s elements into the target and return the target .