My own methods return None instead of a valid value

My own class methods do not work when I check how my function 'linker' operates. These methods return None value.

When I run these methods in the interactive mode, they work and each returns a new node linked to the root. Why do these methods not work when I run the function 'linker'?

class node:
    def init(self, data):
        self.data = data
        self.left = None
        self.right = None

    def insertL(self, data):
        self.left = node(data)
        return self.left

    def insertR(self, data):
        self.right = node(data)
        return self.right

def linker(root, lst):
    import random

   seq = ['left', 'right', 'nither', 'either']
   res = random.choices(seq,(0.1,0.3,0.1,0.6), k=1)
   if lst:
    l=random.choice(lst)

    if res == 'left':
        root=root.insertL(l)
        lst.remove(l)
        return root, lst
    elif res == 'right':
        root=root.insertR(l)
        lst.remove(l)
        return root,lst
    elif res == 'nither':
        return root,lst
    elif res == 'either':
        nodes = [root.insertL(l)]
        lst.remove(l)
        l2=random.choice(lst)
        nodes+=[root.insertR(l2)]
        lst.remove(l2)
        return nodes, lst
   else: return root, lst