code: def nc_filename(tmp_path):
      """Create an nc filename for viirs m band."""
      now = datetime.utcnow()
      filename = f"testingcfwriter{now:%Y%j%H%M%S}-viirs-mband-20201007075915-20201007080744.nc"
      return str(tmp_path / filename)
  
imports: import warnings
  from datetime import datetime
  import numpy
  import pytest
  import xarray
  from pyresample import AreaDefinition, SwathDefinition
  from satpy import Scene
  from satpy.dataset.dataid import WavelengthRange
  from satpy.readers.satpy_cf_nc import SatpyCFFileHandler
label_desc: Use image node_id 3 for calling a global function with example usage: nc_filename(tmp_path) and returns: str