-----Description-----  
This task requires writing a Lean 4 method that determines whether a given non-negative natural number is a perfect square. In other words, the method should return true if there exists a natural number whose square is equal to the input number, and false if no such number exists.

-----Input-----  
The input consists of a single natural number:  
n: A non-negative natural number (Nat).

-----Output-----  
The output is a Boolean value:  
Returns true if there exists an integer such that its square equals the input n.  
Returns false if no integer squared equals the input n.