human
Write me a the Python program you requested given the following:
I am working on the file "Python/Chapter-06/Ordered-Binary-Tree.ipynb".
The first task is:
Ordered Binary Trees
This notebook implements ordered binary trees.  In order to define this notion, we first have to define 
the concept of ordered binary trees.  In the following, assume a set $\texttt{Key}$ and a set $\texttt{Value}$ are given.   Then, the
set $\mathcal{B}$ of all ordered binary trees is defined inductively.
  - $\texttt{Nil} \in \mathcal{B}$
  - $\texttt{Node}(k, v, l, r) \in \mathcal{B}$  iff the following conditions hold:
      - $k \in\texttt{Key}$,
      - $v \in\texttt{Value}$,
      - $l \in\mathcal{B}$,
      - $r \in\mathcal{B}$,
      - all keys that occur in the left subtree $l$ are smaller than $k$,
      - all keys that occur in the right subtree $r$ are bigger than $k$,
    therefore $l &lt.
k &lt.
r$.

The class OrderedBinaryTree represents the nodes of an ordered binary tree.
  - $\texttt{Nil}$           is created as $\texttt{OrderedBinaryTree}()$.
  - $\texttt{Node}(k,v,l,r)$ is created as follows:
    t = OrderedBinaryTree()
    t.mKey   = k
    t.mValue = v
    t.mLeft  = l
    t.mRight = r
The constructor below creates the empty tree.
Can you write Python program for it?
assistant
#Here is the Python program you requested.

class OrderedBinaryTree:
    def __init__(self):
        self.mKey   = None
        self.mValue = None
        self.mLeft  = None
        self.mRight = None