code: def get_earth_radius(lon, lat, a, b):
      """Compute radius of the earth ellipsoid at the given longitude and latitude.
  
      Args:
          lon: Geodetic longitude (degrees)
          lat: Geodetic latitude (degrees)
          a: Semi-major axis of the ellipsoid (meters)
          b: Semi-minor axis of the ellipsoid (meters)
  
      Returns:
          Earth Radius (meters)
  
      """
      geocent = pyproj.CRS.from_dict(
          {"proj": "geocent", "a": a, "b": b, "units": "m"}
      )
      latlong = pyproj.CRS.from_dict(
          {"proj": "latlong", "a": a, "b": b, "units": "m"}
      )
      transformer = pyproj.Transformer.from_crs(latlong, geocent)
      x, y, z = transformer.transform(lon, lat, 0.0)
      return np.sqrt(x**2 + y**2 + z**2)
  
imports: from __future__ import annotations
  import bz2
  import logging
  import os
  import shutil
  import tempfile
  import warnings
  from contextlib import closing, contextmanager
  from io import BytesIO
  from shutil import which
  from subprocess import PIPE, Popen
  import numpy
  import pyproj
  import xarray
  from pyresample.geometry import AreaDefinition
  from satpy import config
  from satpy.readers import FSFile
  from satpy.utils import get_legacy_chunk_size
label_desc: Use image node_id 19 for calling a global function with example usage: get_earth_radius(lon, lat, a, b) and returns: np