code: public static String getExtensionName(GeometryType geometryType) {
  
  		if (!isExtension(geometryType)) {
  			throw new GeoPackageException(GeometryType.class.getSimpleName()
  					+ " is not an extension: " + geometryType.getName());
  		}
  
  		if (!isGeoPackageExtension(geometryType)) {
  			throw new GeoPackageException(
  					GeometryType.class.getSimpleName()
  							+ " is not a GeoPackage extension, User-Defined requires an author: "
  							+ geometryType.getName());
  		}
  
  		String extensionName = GeoPackageConstants.GEO_PACKAGE_EXTENSION_AUTHOR
  				+ Extensions.EXTENSION_NAME_DIVIDER
  				+ GeoPackageConstants.GEOMETRY_EXTENSION_PREFIX
  				+ Extensions.EXTENSION_NAME_DIVIDER + geometryType.getName();
  
  		return extensionName;
  	}
docs: Get the extension name of a GeoPackage extension Geometry
  
  @param geometryType
  geometry type
  @return extension name