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

Given an array arr of integers, check if there exist two indices i and j such that :

i != j
0 <= i, j < arr.length
arr[i] == 2 * arr[j]

 
Please complete the following python code precisely:
```python
class Solution:
    def checkIfExist(self, arr: List[int]) -> bool:
```