code: public static String getSchemaFromType(final Type type, Map<String, Schema> schemaMap, IRestDocGeneratorExtension ext) {
  		String schema = SchemaResolver.getSchemaFromTypeOrNull(type, schemaMap, ext);
  		if (schema != null) {
  			return schema;
  		}
  		final String s = String.format("SchemaType %s is not annotated with RestDocSchema.", type);
  		throw new RestDocException(s);
  	}
docs: same as getSchemaFromClassOrNull but throws {@link RestDocException} if no schema is found
  
  @param type the type to scan
  @param schemaMap the map to add the schema to
  @param ext the IRestDocGeneratorExtension to invoke on new schema
  @return the schema URI