pub fn map<D2, L>(&self, mut logic: L) -> Collection<G, D2, R>
    where D2: Data,
          L: FnMut(D) -> D2 + 'static
    {
        self.inner
            .map(move |(data, time, delta)| (logic(data), time, delta))
            .as_collection()
    }
Creates a new collection by applying the supplied function to each input element.

# Examples

```
use differential_dataflow::input::Input;

::timely::example(|scope| {
scope.new_collection_from(1 .. 10).1
.map(|x| x * 2)
.filter(|x| x % 2 == 1)
.assert_empty();
});
```
differential-dataflow/src/collection.rs