pub fn enter<'a, T>(&self, child: &Child<'a, G, T>) -> Collection<Child<'a, G, T>, D, R>
    where
        T: Refines<<G as ScopeParent>::Timestamp>,
    {
        self.inner
            .enter(child)
            .map(|(data, time, diff)| (data, T::to_inner(time), diff))
            .as_collection()
    }
Brings a Collection into a nested scope.

# Examples

```
use timely::dataflow::Scope;
use differential_dataflow::input::Input;

::timely::example(|scope| {

let data = scope.new_collection_from(1 .. 10).1;

let result = scope.region(|child| {
data.enter(child)
.leave()
});

data.assert_eq(&result);
});
```
differential-dataflow/src/collection.rs