input: Write a function to calculate the square root of a user-defined positive number using the `math.sqrt` function.
  
  def calculate_square_root(n):
      import math
      if n < 0:
          return "Input must be a positive number"
      square_root = math.sqrt(n)
      return square_root
  
  assert calculate_square_root(100) == 10.0
  assert calculate_square_root(25) == 5.0
  assert calculate_square_root(9) == 3.0
  assert calculate_square_root(16) == 4.0
  assert calculate_square_root(0) == 0.0
output: def calculate_square_root(n):
      import math
      if n < 0:
          return "Input must be a positive number"
      square_root = math.sqrt(n)
      return square_root