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

Given an integer array arr, and an integer target, return the number of tuples i, j, k such that i < j < k and arr[i] + arr[j] + arr[k] == target.
As the answer can be very large, return it modulo 109 + 7.
 
Please complete the following python code precisely:
```python
class Solution:
    def threeSumMulti(self, arr: List[int], target: int) -> int:
```