[test] Add test cases of untested functions for BTreeSet - add [`is_superset()`](https://doc.rust-lang.org/std/collections/struct.BTreeSet.html#method.is_superset) and [`remove()`](https://doc.rust-lang.org/std/collections/struct.BTreeSet.html#method.remove) test cases for BTreeSet since these functions has no test cases. |
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| .. | ||
| benches | ||
| src | ||
| tests | ||
| Cargo.toml | ||