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

Given an array rectangles where rectangles[i] = [xi, yi, ai, bi] represents an axis-aligned rectangle. The bottom-left point of the rectangle is (xi, yi) and the top-right point of it is (ai, bi).
Return true if all the rectangles together form an exact cover of a rectangular region.
 
Please complete the following python code precisely:
```python
class Solution:
    def isRectangleCover(self, rectangles: List[List[int]]) -> bool:
```