input: Write a python function to search for a value in a binary tree.
  assert bt.search(bt.root, 4) == True
  assert bt.search(bt.root, 10) == False
  assert bt.search(bt.root, 2) == True
output: class Node:
      def __init__(self, value):
          self.value = value
          self.left = None
          self.right = None
  
  class BinaryTree:
      def __init__(self):
          self.root = None
  
      def insert(self, value):
          if self.root is None:
              self.root = Node(value)
          else:
              self._insert(value, self.root)
  
      def _insert(self, value, node):
          if value < node.value:
              if node.left is None:
                  node.left = Node(value)
              else:
                  self._insert(value, node.left)
          else:
              if node.right is None:
                  node.right = Node(value)
              else:
                  self._insert(value, node.right)
  
      def search(self, node, value):
          if node is None:
              return False
          if node.value == value:
              return True
          elif value < node.value:
              return self.search(node.left, value)
          else:
              return self.search(node.right, value)
  
  # Example usage:
  bt = BinaryTree()
  bt.insert(5)
  bt.insert(3)
  bt.insert(8)
  bt.insert(2)
  bt.insert(4)
  bt.insert(7)
  bt.insert(9)