input: Write a python function to calculate wind chill based on given temperature and wind speed.
  assert calc_windchill(0, 10) == -4.875
  assert calc_windchill(5, 20) == -0.478
  assert calc_windchill(15, 10) == 15
  assert calc_windchill(-10, 30) == -18.126
output: def calc_windchill(temperature, wind_speed):
      if wind_speed < 3:
          return temperature
      wind_chill = 35.74 + 0.6215 * temperature - 35.75 * wind_speed**0.16 + 0.4275 * temperature * wind_speed**0.16
      return round(wind_chill, 3)