input: Write a python function to perform basic arithmetic operations: add, subtract, multiply, and divide.
  assert perform_operation(1, 10, 5) == 15
  assert perform_operation(2, 10, 5) == 5
  assert perform_operation(3, 10, 5) == 50
  assert perform_operation(4, 10, 5) == 2.0
  assert perform_operation(5, 10, 5) == "Invalid operation"
output: def perform_operation(op, a, b):
      if op == 1:
          return a + b
      elif op == 2:
          return a - b
      elif op == 3:
          return a * b
      elif op == 4:
          return a / b
      else:
          return "Invalid operation"