input: from typing import List, Union
  
  def find_index(arr: List[Union[int, float]], x: Union[int, float]) -> int:
      """Find and return the index of element x in given array arr.
      If the element is not found, return -1.
      >>> find_index([2, 5, 9, 15], 5)
      1
      >>> find_index([2, 5, 9, 15], 20)
      -1
      """
      for i in range(len(arr)):
          if arr[i] == x:
              return i
      return -1
output:     for i in range(len(arr)):
          if arr[i] == x:
              return i
      return -1