input: 
  def are_similar(root1, root2):
      """ Compares two binary trees to check if they are similar. Two trees are considered similar if they have
      the same structure and corresponding nodes have the same value. 
      >>> from instruction_input import TreeNode
      >>> root1 = TreeNode(1)
      >>> root1.left, root1.right = TreeNode(2), TreeNode(3)
      >>> root2 = TreeNode(1)
      >>> root2.left, root2.right = TreeNode(2), TreeNode(3)
      >>> are_similar(root1, root2)
      True
      >>> root3 = TreeNode(1)
      >>> root3.left, root3.right = TreeNode(3), TreeNode(2)
      >>> are_similar(root1, root3)
      False
      """
      if root1 is None and root2 is None:
          return True
      if root1 is None or root2 is None:
          return False
      if root1.val != root2.val:
          return False
      return are_similar(root1.left, root2.left) and are_similar(root1.right, root2.right)
  
output:     if root1 is None and root2 is None:
          return True
      if root1 is None or root2 is None:
          return False
      if root1.val != root2.val:
          return False
      return are_similar(root1.left, root2.left) and are_similar(root1.right, root2.right)