code: def __init__(self, rule, output):
      self.output = output
      self.rule = rule
  
file_path: snakemake/snakemake/checkpoints.py
imports: from snakemake.common import async_run
  from snakemake.exceptions import IncompleteCheckpointException, WorkflowError
  from snakemake.io import checkpoint_target
label_desc: Use image node_id 1 to create a new CheckpointJob object  with example: obj = CheckpointJob(rule, output)