input: Write a python function to multiply two numbers and print the result.
  assert multiply(2, 3) == "Result is:  6"
  assert multiply(5, 5) == "Result is:  25"
  assert multiply(10, -2) == "Result is:  -20"
output: def multiply(a, b):
      result = a * b
      return f"Result is:  {result}"