docs: def get_unitless_standard_names():
      '''
      Returns a list of valid standard_names that are allowed to be unitless
      '''
      global _UNITLESS_DB
      if _UNITLESS_DB is None:
          with open(resource_filename('cc_plugin_ncei', 'data/unitless.json'), 'r') as f:
              _UNITLESS_DB = json.load(f)
      return _UNITLESS_DB