Given 2 binary trees `t` and `s`, find if `s` has an equal subtree in `t`,
where the structure and the values are the same. Return `True` if it
exists, otherwise return `False`.

Here's some starter code and an example:

```python
class Node:
  def __init__(self, value, left=None, right=None):
    self.value = value
    self.left = left
    self.right = right
  def __repr__(self):
    return f"(Value: {self.value} Left: {self.left} Right: {self.right})"
def
  find_subtree(s, t):
  # Fill this in.
t3 = Node(4, Node(3), Node(2))
t2 = Node(5, Node(4), Node(-1))
t = Node(1, t2, t3)
s = Node(4, Node(3), Node(2))
"""
Tree t:
    1
   / \
  4   5
 / \ / \
3  2 4 -1
Tree s:
  4
 / \
3  2
"""
print(find_subtree(s, t))
# True
```