code: def get_parent_id(chebi_id):
      '''Returns parent id'''
      if len(__PARENT_IDS) == 0:
          __parse_compounds()
  
      return __PARENT_IDS[chebi_id] if chebi_id in __PARENT_IDS else float('NaN'f get_parent_id(chebi_id):
      '''Returns parent id'''
      if len(__PARENT_IDS) == 0:
          __parse_compounds()
  
      return __PARENT_IDS[chebi_id] if chebi_id in __PARENT_IDS else float('NaN')
docs: Returns parent id