input: Write a function to find the minimum value in an array.
  assert find_min([3, 9, 0, 7, 88]) == 0
  assert find_min([1, 2, 3, 4, 5]) == 1
  assert find_min([-1, -2, -3, -4, -5]) == -5
output: def find_min(arr):
      return min(arr)