[Python-ideas] Enum: determining if a value is valid

A question that comes up quite a bit on Stackoverflow is how to test to see if a value will result in an Enum member, preferably without having to go through the whole try/except machinery.

A couple versions ago one could use a containment check:

if 1 in Color:

but than was removed as Enums are considered containers of members, not containers of the member values. It was also possible to define one's own `_missing_` method and have it return None or the value passed in, but that has also been locked down to either return a member or raise an exception.

At this point I see three options:

1) add a `get(value, default=None)` to EnumMeta (similar to `dict.get()`

2) add a recipe to the docs

3) do nothing

Thoughts?

-- ~Ethan~