docs: def planetType(temperature, mass, radius):
      """ Returns the planet type as 'temperatureType massType'
      """
  
      if mass is not np.nan:
          sizeType = planetMassType(mass)
      elif radius is not np.nan:
          sizeType = planetRadiusType(radius)
      else:
          return None
  
      return '{0} {1}'.format(planetTempType(temperature), sizeType)