Write a function to search for a value in a binary search tree.
user
def search_bst(root, value):
    # Check if the root is null
    if root is None:
        return False

    # If the value is at the root, return True
    if root.value == value:
        return True

    # Search the left or right subtree based on the value
    if value < root.value:
        return search_bst(root.left, value)
    else:
        return search_bst(root.right, value)
assistant