input: Write a function to take a list of numbers and return the sum of the numbers. The function should iterate through each number in the list and add it to a running total; finally, it should return the total sum. If the list is empty, the function should return 0.
  
  sum_list([1,2,3,4,5])
output: def sum_list(numbers):
      total = 0
      for num in numbers:
          total += num
      return total