input: Write a function to calculate the square root of a user-defined positive number using the math library. The function should return the square root if the input is valid, otherwise return an error message.
  assert square_root(100) == 10.0
  assert square_root(25) == 5.0
  assert square_root(0) == "Error: The input must be a positive number"
  assert square_root(-1) == "Error: The input must be a positive number"
output: def square_root(num):
      if num < 0:
          return "Error: The input must be a positive number"
      return math.sqrt(num)