input: Write a python function to calculate BMI from weight and height.
  assert calculate_bmi(70, 1.80) == 21.60
  assert calculate_bmi(80, 1.75) == 26.12
  assert calculate_bmi(60, 1.65) == 22.04
output: def calculate_bmi(weight, height):
      bmi = weight / (height ** 2)
      return round(bmi, 2)