def hello_world():
    print("Hello, World!")
    return True

def fibonacci(n):
    if n <= 1:
        return n
    return fibonacci(n-1) + fibonacci(n-2)

def factorial(n):
    if n == 0:
        return 1
    return n * factorial(n-1)

class Calculator:
    def __init__(self):
        self.result = 0
    
    def add(self, a, b):
        return a + b
    
    def subtract(self, a, b):
        return a - b

def bubble_sort(arr):
    n = len(arr)
    for i in range(n):
        for j in range(0, n-i-1):
            if arr[j] > arr[j+1]:
                arr[j], arr[j+1] = arr[j+1], arr[j]
    return arr

def binary_search(arr, target):
    left, right = 0, len(arr) - 1
    while left <= right:
        mid = (left + right) // 2
        if arr[mid] == target:
            return mid
        elif arr[mid] < target:
            left = mid + 1
        else:
            right = mid - 1
    return -1

def is_palindrome(s):
    s = s.lower()
    return s == s[::-1]

def sum_list(numbers):
    total = 0
    for num in numbers:
        total += num
    return total