Please solve the programming task below using a self-contained code snippet in a markdown code block.

You have k lists of sorted integers in non-decreasing order. Find the smallest range that includes at least one number from each of the k lists.
We define the range [a, b] is smaller than range [c, d] if b - a < d - c or a < c if b - a == d - c.
 
Please complete the following python code precisely:
```python
class Solution:
    def smallestRange(self, nums: List[List[int]]) -> List[int]:
```