old_contents: def convert_cholesterol_unit(value, from_unit, to_unit):
      if from_unit.lower() == to_unit.lower():
          return value
      elif to_unit.lower() == 'mmol/l':
          return value * 0.02586
      elif to_unit.lower() == 'mg/dl':
          return value * 88.57
      else:
          return None
  
  
  def convert_weight_unit(value, from_unit, to_unit):
      raise NotImplementedError('use "helpers.converter.WeightConverter"')
  
  
  def convert_height_unit(value, from_unit, to_unit):
      raise NotImplementedError('use "helpers.converter.HeightConverter"')
  
new_contents: def convert_cholesterol_unit(value, from_unit, to_unit):
      raise NotImplementedError('use "helpers.converter.CholesterolConverter"')
  
  
  def convert_weight_unit(value, from_unit, to_unit):
      raise NotImplementedError('use "helpers.converter.WeightConverter"')
  
  
  def convert_height_unit(value, from_unit, to_unit):
      raise NotImplementedError('use "helpers.converter.HeightConverter"')
  
subject: remove convert_cholesterol_unit method