input: Write a function to improve the given function by using Python built-in functions. The original function takes in an array of numbers and returns the sum of all the numbers by iterating through the array and summing each element manually. The improved function should replace the manual summation with a built-in Python function that achieves the same result.
  
  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([-1, -2, -3, -4, -5])==-15
  assert sum_array([10])==10
output: def sum_array(array):
      return sum(array)