Pythonic Linked List

gistfile1.py

class Tree(object):
    def __init__(self, root=None):
        self.root = root

    @classmethod
    def from_string(cls, tree_string):
        raise NotImplementedError
        
    def __contains__(self, item):
        if isinstance(item, Node):
            return self._node_exists(item)
        elif isinstance(item, Tree):
            ##This either will get really messy or work perfectly
            return self._node_exists(item.root)
        else:
            return self.lookup(item)
        
    def _node_exists(self, item):
        if self.root == item:
            return True
        elif item.value <= self.root.value and self.root.left is not None:
            return Tree(self.root.left)._node_exists(item)
        elif item.value > self.root.value and self.root.right is not None:
            return Tree(self.root.right)._node_exists(item)
        else:
            return False
            
    def lookup(self, item):
        raise NotImplementedError
        
    def insert(self, value):
        if self.root is None:
            print 'Root is None - Creating Root'
            self.root = Node(value)
        elif value <= self.root.value and self.root.left is None:
            print 'Left Node Acquired'
            self.root.left = Node(value)
        elif value <= self.root.value:
            print 'Going to the Left Node'
            Tree(self.root.left).insert(value)
        elif self.root.right is None:
            print 'Right Node Acquired'
            self.root.right = Node(value)
        else:
            print 'Going to the Right Node'
            Tree(self.root.right).insert(value)

            
class Node(object):
    def __init__(self, value, left=None, right=None):
        
        assert isinstance(left, Node) or left is None
        assert isinstance(right, Node) or right is None
        

        self.value = value
        self.left = left
        self.right = right

        
    def __eq__(self, other):
        if other:
            return all((self.value == other.value,
                        self.left == other.left,
                        self.right == other.right))
        else:
            return False
    

if __name__ == '__main__':
    n1 = Node(1, None, None)
    n2 = Node(2, n1, None)
    n3 = Node(2, n1, None)
    
    #import pdb
    #pdb.set_trace()
    
    print n2 == n3
    print n2 == n1
    
    tree = Tree()
    tree.insert(5)
    tree.insert(7)
    tree.insert(3)
    tree.insert(27)
    tree.insert(5)
    
    t2 = Tree()
    t2.insert(7)
    t2.insert(27)
    t2.insert(5)
    
    import pdb; pdb.set_trace()
    
    print t2 in tree
    
    n4 = Node(27)
    n5 = Node(5)
    n6 = Node(7, n5, n4)
    
    print n6 in t2
    print n6 in tree
    
    
    

I would break this code apart onto 3 files :)