code: def radiance_to_bt(arr, wc_, a__, b__):
      """Convert to BT in K."""
      return a__ + b__ * (
          C2 * wc_ / (da.log(1 + (C1 * (wc_**3) / arr)))
      )
  
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 1 for calling a global function with example usage: radiance_to_bt(arr, wc_, a__, b__) and returns: unknown