docs: def validate_gps(value):
      """Validate GPS value."""
      try:
          latitude, longitude, altitude = value.split(',')
          vol.Coerce(float)(latitude)
          vol.Coerce(float)(longitude)
          vol.Coerce(float)(altitude)
      except (TypeError, ValueError, vol.Invalid):
          raise vol.Invalid(
              'GPS value should be of format "latitude,longitude,altitude"')
      return value