input: Write a python function to convert temperature between Celsius, Fahrenheit, and Kelvin.
  assert convertTemp(100, 'C', 'F') == 212.0
  assert convertTemp(0, 'C', 'K') == 273.15
  assert convertTemp(32, 'F', 'C') == 0.0
  assert convertTemp(273.15, 'K', 'C') == 0.0
  assert convertTemp(373.15, 'K', 'F') == 212.0
output: def convertTemp(value, from_scale, to_scale):
      if from_scale == 'C':
          if to_scale == 'F':
              return value * 9/5 + 32
          elif to_scale == 'K':
              return value + 273.15
      elif from_scale == 'F':
          if to_scale == 'C':
              return (value - 32) * 5/9
          elif to_scale == 'K':
              return (value - 32) * 5/9 + 273.15
      elif from_scale == 'K':
          if to_scale == 'C':
              return value - 273.15
          elif to_scale == 'F':
              return (value - 273.15) * 9/5 + 32
      return None