Hi, I am wondering about the way `Flatten()` and `FlatMap()` are implemented in Apache Beam Python. In most functional languages, FlatMap() is the same as composing `Flatten()` and `Map()` as indicated by the name, so Flatten() and Flatmap() have the same input. But in Apache Beam, Flatten() is using _iterable of PCollections_ while FlatMap() is working with _PCollection of Iterables_.
If I am not wrong, the signature of Flatten, Map and FlatMap are : ``` Flatten:: Iterable[PCollections[A]] -> PCollection[A] Map:: (PCollection[A], (A-> B)) -> PCollection[B] FlatMap:: (PCollection[Iterable[A]], (A->B)) -> [A] ``` So my question is is there another "Flatten-like" function with this signature : ``` anotherFlatten:: PCollection[Iterable[A]] -> PCollection[A] ``` One of the reason this would be useful, is that when you just want to "flatten" a `PCollection` of `iterable` you have to use `FlatMap()`with an identity function. So instead of writing: `FlatMap(lambda e: e)` I would like to use a function `anotherFlatten()` Thanks, Godefroy
