code: def test_verticalcs_height_to_cf():
      vcs = VerticalCS(axis=VerticalCSAxis.GRAVITY_HEIGHT_US_FT)
      vcs.to_cf() == [
          {
              "standard_name": "height_above_reference_ellipsoid",
              "long_name": "Gravity-related height",
              "units": "0.304800609601219 metre",
              "positive": "up",
              "axis": "Z",
          }
      ]
  
file_path: pyproj/test/crs/test_crs_coordinate_system.py
imports: import pytest
  from pyproj.crs.coordinate_system import Cartesian2DCS, Ellipsoidal2DCS, Ellipsoidal3DCS, VerticalCS
  from pyproj.crs.enums import Cartesian2DCSAxis, Ellipsoidal2DCSAxis, Ellipsoidal3DCSAxis, VerticalCSAxis
label_desc: Use image node_id 10 for calling a global function with example usage: test_verticalcs_height_to_cf() without return types