[Python] Recursive insert method on Binary Tree reaches the correct node but it doesn't save...

I'm trying to make a recursive insert method on a binary tree and while the recursive part of the function seems to do the job correctly (I tracked the code step by step with debug option) when time comes for data to be saved it just doesn't happen. Is it a reference mistake?

class TreeNode:
def __init__(self, data=None, left=None, right=None):
self.data = data
self.left = left
self.right = right

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

def insert(self, data):

def in_insert(node, data):
if node is None:
node = TreeNode(data)
elif node.data == data:
print(f'{node.data} already in here.')
elif node.data > data:
node = node.left
in_insert(node, data)`
else:
node = node.right
in_insert(node, data)

if self.root is None:
self.root = TreeNode(data)
else:
in_insert(self.root, data)

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