input: Write a function to find the index of a given value in an array. If the value is present, return its index; otherwise, return -1. The array may contain duplicate values, but the function should return the index of the first occurrence of the value.
  
  
  assert find_index([2, 5, 9, 15], 5) == 1
  assert find_index([2, 5, 9, 15], 9) == 2
  assert find_index([2, 5, 9, 15], 20) == -1
  assert find_index([2, 5, 9, 5, 15], 5) == 1
  assert find_index([], 5) == -1
  
output: def find_index(arr, value):
      try:
          return arr.index(value)
      except ValueError:
          return -1