code: def get_mass(chebi_id):
      '''Returns mass'''
      if len(__MASSES) == 0:
          __parse_chemical_data()
  
      return __MASSES[chebi_id] if chebi_id in __MASSES else float('NaN'f get_mass(chebi_id):
      '''Returns mass'''
      if len(__MASSES) == 0:
          __parse_chemical_data()
  
      return __MASSES[chebi_id] if chebi_id in __MASSES else float('NaN')
docs: Returns mass