Hello guys, I need to test if a value is contained in a MutableBinaryHeap.

I may have the following Tuple t:

```
6-element Vector{Tuple{Int64, Float64}}:
(1, Inf)
(2, Inf)
(3, Inf)
(4, Inf)
(5, Inf)
(6, Inf)
```

For the Tuple case I can just do:

```
a=first.(t)
```

And check whether a value is contained in a.

The problem is that I need to do this test on a MutableBinaryHeap.

I have the heap h

```
MutableBinaryHeap((1, 0.0), (2, Inf), (3, Inf), (4, Inf), (5, Inf), (6, Inf))
```

and doing

```
c=first.(h)
```

gives the following error:

```
ERROR: MethodError: no method matching iterate(::MutableBinaryHeap{Tuple{Int64, Float64}, Base.Order.By{typeof(last), Base.Order.ForwardOrdering}})
```

Any idea on how to test is a value is contained on the first element of a MutableBinaryHeap?

Thank you so much in advance.