code: def generate_imapp_filename(suffix):
      """Generate a filename that follows IMAPP MODIS L1b convention."""
      now = datetime.now()
      return f"t1.{now:%y%j.%H%M}.{suffix}.hdf"
  
imports: from __future__ import annotations
  from datetime import datetime, timedelta
  from typing import Optional
  import numpy
  import pytest
  from pyhdf.SD import SD, SDC
label_desc: Use image node_id 12 for calling a global function with example usage: generate_imapp_filename(suffix) and returns: str, now, str, suffix, str