code: def load_included_indentifiers(self, file_name):
          '''Loads a file with newline-separated integers representing which 
          chemical should be kept in memory; ones not included are ignored.
          '''
          self.restrict_identifiers = True
          included_identifiers = set()       
          with open(file_name) as f:
              [included_identifiers.add(int(line)) for line in f]
          self.included_identifiers = included_identifierf load_included_indentifiers(self, file_name):
          '''Loads a file with newline-separated integers representing which 
          chemical should be kept in memory; ones not included are ignored.
          '''
          self.restrict_identifiers = True
          included_identifiers = set()       
          with open(file_name) as f:
              [included_identifiers.add(int(line)) for line in f]
          self.included_identifiers = included_identifiers
docs: Loads a file with newline-separated integers representing which 
          chemical should be kept in memory; ones not included are ignored.