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

Given an n x n binary matrix grid, return the length of the shortest clear path in the matrix. If there is no clear path, return -1.
A clear path in a binary matrix is a path from the top-left cell (i.e., (0, 0)) to the bottom-right cell (i.e., (n - 1, n - 1)) such that:

All the visited cells of the path are 0.
All the adjacent cells of the path are 8-directionally connected (i.e., they are different and they share an edge or a corner).

The length of a clear path is the number of visited cells of this path.
 
Please complete the following python code precisely:
```python
class Solution:
    def shortestPathBinaryMatrix(self, grid: List[List[int]]) -> int:
```