input: Write a function to improve the given function using Python built-in functions. The original function takes in an array of numbers and returns the sum of all the numbers. The improvement should replace the loop with a built-in function.
  
  def sum_array(array):
      '''A function that takes in an array of numbers and returns the sum of all the numbers'''
      return sum(array)
  
  assert sum_array([1, 2, 3, 4, 5]) == 15
  assert sum_array([10, 20, 30]) == 60
  assert sum_array([-1, -2, -3, -4, -5]) == -15
  assert sum_array([]) == 0
  assert sum_array([5]) == 5
output: def sum_array(array):
      return sum(array)