class_docstr: Eps level 1b reader for AVHRR data.
docstr: Mask for 3B.
code: def three_b_mask(self):
      """Mask for 3B."""
      return (self["FRAME_INDICATOR"] & 2**16) != 0
  
imports: import functools
  import logging
  import dask.array
  import numpy
  import xarray
  from dask.delayed import delayed
  from pyresample.geometry import SwathDefinition
  from satpy._compat import cached_property
  from satpy._config import get_config_path
  from satpy.readers.file_handlers import BaseFileHandler
  from satpy.readers.xmlformat import XMLFormat
  from satpy.utils import get_legacy_chunk_size
label_desc: Use image node_id 14 for calling the EPSAVHRRFile obj's underlying member method code with example usage: obj.three_b_mask() and returns: unknown