fn deref(&self) -> &T {
        debug_assert!(!self.heap.is_empty());
        // SAFE: PeekMut is only instantiated for non-empty heaps
        unsafe { self.heap.data.get_unchecked(0) }
    }
Returns a mutable reference to the greatest item in the binary heap, or
`None` if it is empty.

Note: If the `PeekMut` value is leaked, the heap may be in an
inconsistent st
benchmarks/haystacks/code/rust-library.rs