class_docstr: Generic GRIB file handler.
class_docstr_tok: ["Generic","GRIB","file","handler","."]
code: def _convert_datetime(
      msg, date_key, time_key, date_format="%Y%m%d%H%M"
  ):
      date_str = "{:d}{:04d}".format(msg[date_key], msg[time_key])
      return datetime.strptime(date_str, date_format)
  
imports: import logging
  from datetime import datetime
  import dask.array
  import numpy
  import pygrib
  import xarray
  from pyproj import Proj
  from pyresample import geometry
  from satpy.dataset import DataQuery
  from satpy.readers.file_handlers import BaseFileHandler
  from satpy.utils import get_legacy_chunk_size
label_desc: Use image node_id 4 for calling the GRIBFileHandler obj's underlying member method code with example usage: obj._convert_datetime(msg, date_key, time_key, date_format) and returns: datetime