code: def get_all_modified_on(chebi_ids):
      '''Returns all modified on'''
      all_modified_ons = [get_modified_on(chebi_id) for chebi_id in chebi_ids]
      all_modified_ons = [modified_on for modified_on in all_modified_ons
                          if modified_on is not None]
      return None if len(all_modified_ons) == 0 else sorted(all_modified_ons)[-1f get_all_modified_on(chebi_ids):
      '''Returns all modified on'''
      all_modified_ons = [get_modified_on(chebi_id) for chebi_id in chebi_ids]
      all_modified_ons = [modified_on for modified_on in all_modified_ons
                          if modified_on is not None]
      return None if len(all_modified_ons) == 0 else sorted(all_modified_ons)[-1]
docs: Returns all modified on