code: def test_LatitudeFormatter_degree_symbol():
      formatter = LatitudeFormatter(degree_symbol="")
      p = ccrs.PlateCarree()
      formatter.set_axis(Mock(axes=Mock(GeoAxes, projection=p)))
      test_ticks = [-90, -60, -30, 0, 30, 60, 90]
      result = [formatter(tick) for tick in test_ticks]
      expected = ["90S", "60S", "30S", "0", "30N", "60N", "90N"]
      assert result == expected
  
imports: from unittest.mock import Mock
  import matplotlib.pyplot
  import numpy
  import pytest
  import cartopy.crs
  from cartopy.mpl.geoaxes import GeoAxes
  from cartopy.mpl.ticker import LatitudeFormatter, LatitudeLocator, LongitudeFormatter, LongitudeLocator
label_desc: Use image node_id 4 for calling a global function with example usage: test_LatitudeFormatter_degree_symbol() without return types