input: Write a function to approximate the value of π using the Monte Carlo method.
  assert round(3.1 <= approx_pi(1000) <= 3.2, 1)
  assert round(3.12 <= approx_pi(10000) <= 3.16, 2)
  assert round(3.13 <= approx_pi(100000) <= 3.15, 2)
output: import random
  
  def approx_pi(num_samples):
      inside_circle = 0
      for _ in range(num_samples):
          x, y = random.uniform(0, 1), random.uniform(0, 1)
          if x**2 + y**2 <= 1:
              inside_circle += 1
      return (inside_circle / num_samples) * 4