I have a list of the form -

```
a_list = [[1, [2, 3, 4]], [2, [3, 4]], [3, [4]]]

```

I want to convert it to the form -

```
b_list = [[1,2],[1,3],[1,4],[2,3],[2,4],[3,4]]

```

Using the list comprehension, I have tried with below code 

```
for lst in tup:
    for lst1 in tup[1]:
        tup2 = [lst[0],lst1]

```

and getting (which is wrong)- 

```
tup2 = [3, [3, 4]]

```

Please help, Thanks in advance