code: def test_user_agent_custom(self):
      geocoder = ArcGIS(user_agent="my_user_agent/1.0")
      assert geocoder.headers["User-Agent"] == "my_user_agent/1.0"
  
file_path: geopy/test/geocoders/arcgis.py
imports: import pytest
  from geopy import exc
  from geopy.geocoders import ArcGIS
  from geopy.point import Point
  from test.geocoders.util import BaseTestGeocoder, env
label_desc: Use image node_id 1 for calling the TestUnitArcGIS obj's underlying member method code with example usage: obj.test_user_agent_custom() without return types