human
I am working on the file "Python/Chapter-07/Heap.ipynb".
The first task is:
Defining $\texttt{Nil}$ and $\texttt{Node}(p, v, l, r)$ as Classes
The class Nil represents an empty heap.
Can you write Python program for it?
assistant
#Here is the Python program you requested.

class Nil(Heap):
    def _count(self):
        return 0
    
    def __str__(self):
        return 'Nil()'