private long fibonacci(int n) {
        if (n <= 1) {
            return n;
        }
        long prev = 0, curr = 1;
        for (int i = 2; i <= n; i++) {
            long temp = curr;
            curr = curr + prev;
            prev = temp;
        }
        return curr;
    }
FibonacciFunction  ->  fibonacci(numeric)
Description:
- Return NULL if 'numeric' is NULL;
- Returns the nth Fibonacci number
inlong-sdk/transform-sdk/src/main/java/org/apache/inlong/sdk/transform/process/function/arithmetic/FibonacciFunction.java