input: Write a function to calculate the square root of a given number using the Newton-Raphson method.
  assert square_root(36) == 6.0
  assert square_root(49) == 7.0
  assert square_root(100) == 10.0
output: def square_root(n, tolerance=1e-10):
      guess = n / 2.0
      while True:
          new_guess = (guess + n / guess) / 2.0
          if abs(new_guess - guess) < tolerance:
              return new_guess
          guess = new_guess