input: Write a function to find the index of a given value in an array. If the value is present in the array, the function should return its index; otherwise, it should return -1.
  assert find_index([2, 5, 9, 15], 5)==1
  assert find_index([2, 5, 9, 15], 10)==-1
  assert find_index([], 5)==-1
  assert find_index([1, 2, 3, 4], 4)==3
  assert find_index([1, 2, 3, 4], 1)==0
output: def find_index(arr, value):
      try:
          return arr.index(value)
      except ValueError:
          return -1