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

You have some coins.  The i-th coin has a probability prob[i] of facing heads when tossed.
Return the probability that the number of coins facing heads equals target if you toss every coin exactly once.
 
Please complete the following python code precisely:
```python
class Solution:
    def probabilityOfHeads(self, prob: List[float], target: int) -> float:
```