# Objective
The schedule graph can easily confirm whether a set is contained or not.
This helps me in my personal project where I write an extension trait
for `Schedule` and I want to configure a specific set in its methods.
The set in question has a run condition though and I don't want to add
that condition to the same schedule as many times as the trait methods
are called. Since the non-pub set is unknown to the schedule until then,
a `contains_set` is sufficient.
It is probably trivial to add a method that returns an `Option<NodeId>`
as well but as I personally don't need it I did not add that. If it is
desired I can do so here though. It might be unneeded to have a
`contains_set` then because one could check `is_some` on the returned id
in that case.
An argument against that is that future changes may be easier if only a
`contains_set` needs to be ported.
## Solution
Added `ScheduleGraph::contains_set`.
## Testing
I put the below showcase code into a temporary unit test and it worked.
If wanted I add it as a test too but I did not see that other more
somewhat complicated methods have tests
---
## Showcase
```rs
#[derive(ScheduleLabel, Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
struct MySchedule;
#[derive(SystemSet, Debug, Default, Clone, Copy, PartialEq, Eq, Hash)]
struct MySet;
let mut schedule = Schedule::new(MySchedule);
assert_eq!(schedule.graph().contains_set(MySet), false);
schedule.configure_sets(MySet);
assert_eq!(schedule.graph().contains_set(MySet), true);
```
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