input: Write a function to calculate the sum of a sequence of integers. The function should iterate through the list of integers and accumulate the sum of all elements. If the sequence is empty, the function should return 0.
  def sum_sequence(sequence):
    sum = 0
    for num in sequence:
      sum += num
    return sum
  assert sum_sequence([1, 2, 3, 4, 5])==15
  assert sum_sequence([-1, 0, 1])==0
  assert sum_sequence([10])==10
  assert sum_sequence([])==0
output: def sum_sequence(sequence):
    sum = 0
    for num in sequence:
      sum += num
    return sum