input: Write a function to sort an array in ascending order using Python. The function should take an array as input and return the sorted array. If the array is empty, it should return an empty array.
  
  def sort_ascending(array):
    array.sort()
    return array
  
  assert sort_ascending([10, 3, 9, 1, 15, 2])==[1, 2, 3, 9, 10, 15]
  assert sort_ascending([])==[]
output: def sort_ascending(array):
    array.sort()
    return array