How many unique lists of 4 numbers can I create where I must choose 1 number from each of the following 4 lists? The first number in the created list must come from list1. The second number in the created list must come from list2. The third number in the created list must come from list3. The fourth number in the created list must come from list4.

list1 = [1, 2, 3]
list2 = [1, 2, 3]
list3 = [1, 2, 3, 4, 5, 6, 7]
list4 = [1, 2, 3, 4, 5, 6, 7]

The following examples of unique lists are allowed:

[1, 2, 7, 6]
[1, 1, 1, 1]
[1, 2, 1, 1]
[2, 1, 1, 1]
[3, 3, 7, 3]

Which python function should help me to generate all these unique lists?