closest binary search tree value II

def find_next_node(self, currentnode, root):
        if currentnode is None or (currentnode.right is None and currentnode == root):
            return None
        if currentnode.right:
            temp = currentnode.right
            while temp.left:
                temp = temp.left
            return temp
        else:
            temp, lastnode = root, None
            while temp is not None and temp != currentnode:
                if temp.val > currentnode.val:
                    lastnode = temp
                    temp = temp.left
                elif temp.val < currentnode.val:
                    temp = temp.right
            return lastnode
            
    def find_previous_node(self, currentnode, root):
        if currentnode is None or (currentnode.left is None and currentnode == root):
            return None
        if currentnode.left:
            temp = currentnode.left
            while temp.right:
                temp = temp.right
            return temp
        else:
            temp, lastnode = root, None
            while temp is not None and temp != currentnode:
                if temp.val > currentnode.val:
                    temp = temp.left
                elif temp.val < currentnode.val:
                    lastnode = temp
                    temp = temp.right
            return lastnode
        
    """
    @param root: the given BST
    @param target: the given target
    @param k: the given k
    @return: k values in the BST that are closest to the target
    """
    def closestKValues(self, root, target, k):
        # write your code here
        result, temp, start_pointer, previous_pointer, next_pointer = [], root, None, None, None
        
        while temp is not None:
            start_pointer = temp
            
            if temp.val > target:
                temp = temp.left
            
            elif temp.val < target:
                temp = temp.right
            
            else:
                break
            
        if start_pointer is not None:
            
            if start_pointer.val > target:
                previous_pointer = self.find_previous_node(start_pointer, root)
                next_pointer = start_pointer
            
            elif start_pointer.val < target:
                previous_pointer = start_pointer
                next_pointer = self.find_next_node(start_pointer, root)
            
            else:
                k -= 1
                result.append(start_pointer.val)
                previous_pointer, next_pointer = self.find_previous_node(start_pointer, root), self.find_next_node(start_pointer, root)
            
            for i in range(k):
                
                if previous_pointer is not None and next_pointer is not None:
                
                    if abs(next_pointer.val - target) >= abs(previous_pointer.val - target):
                        result.append(previous_pointer.val)
                        previous_pointer = self.find_previous_node(previous_pointer, root)
                
                    else:
                        result.append(next_pointer.val)
                        next_pointer = self.find_next_node(next_pointer, root)
                
                elif previous_pointer is not None:
                    result.append(previous_pointer.val)
                    previous_pointer = self.find_previous_node(previous_pointer, root)
                
                elif next_pointer is not None:
                    result.append(next_pointer.val)
                    next_pointer = self.find_next_node(next_pointer, root)
        
        return result