BinaryHeap.capacity
size_t capacity() @propertyReturns the _capacity of the heap, which is the length of the underlying store (if the store is a range) or the _capacity of the underlying store (if the store is a container).
size_t capacity() @propertyReturns the _capacity of the heap, which is the length of the underlying store (if the store is a range) or the _capacity of the underlying store (if the store is a container).