input: Write a function to improve the given function by using Python built-in functions. The original function, named `sum_array`, takes an array of numbers and returns the sum of all the numbers. The improved function should achieve the same result more efficiently.
  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([0, -1, 1])==0
  assert sum_array([])==0
  assert sum_array([-5, -3, -1])==-9
  assert sum_array([10])==10
output: def sum_array(array):
      return sum(array)