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

The Tribonacci sequence Tn is defined as follows: 
T0 = 0, T1 = 1, T2 = 1, and Tn+3 = Tn + Tn+1 + Tn+2 for n >= 0.
Given n, return the value of Tn.
 
Please complete the following python code precisely:
```python
class Solution:
    def tribonacci(self, n: int) -> int:
```