input: Write a function to find the sum of a given list of numbers.
  
  def sum_list(arr):
      """Finds the sum of a given list of numbers.
      
      Args:
          arr (list): List of numbers.
          
      Returns:
          int: Sum of list elements.
      """
      sum = 0
      for num in arr:
          sum += num
      return sum
  
  assert sum_list([1, 2, 3, 4, 5]) == 15
  assert sum_list([10, 20, 30]) == 60
  assert sum_list([]) == 0
  assert sum_list([-1, -2, -3, -4, -5]) == -15
  assert sum_list([5]) == 5
output: def sum_list(arr):
      sum = 0
      for num in arr:
          sum += num
      return sum