input: Write a function to improve the given function by using Python built-in functions. The given function is a function that takes in an array of numbers and returns the sum of all the numbers. If the given array is empty then return 0.
  assert sum_array([1, 2, 3, 4])==10
  assert sum_array([-1, -2, -3, -4])==-10
  assert sum_array([])==0
  assert sum_array([0, 0, 0, 0, 0])==0
  
  def sum_array(array):
      '''A function that takes in an array of numbers and returns the sum of all the numbers'''
      return sum(array)
output: def sum_array(array):
      '''A function that takes in an array of numbers and returns the sum of all the numbers'''
      return sum(array)