input: Write a function to calculate the square root of a user-defined positive number. The function should accept a single integer as input and return the square root of that number. If the input number is not positive, the function should return an error message.
  
  
  assert sqrt_calculator(100)==10.0
  assert sqrt_calculator(25)==5.0
  assert sqrt_calculator(64)==8.0
  assert sqrt_calculator(-4)=="Input must be a positive number"
  assert sqrt_calculator(0)=="Input must be a positive number"
  
output: def sqrt_calculator(num):
      if num <= 0:
          return "Input must be a positive number"
      return num ** 0.5