code: def register_standard (id, source_types, target_types, requirements = []):
      
      g = Generator (id, False, source_types, target_types, requirements)
      register (g)
      return g
docs: Creates new instance of the 'generator' class and registers it.
          Returns the creates instance.
          Rationale: the instance is returned so that it's possible to first register
          a generator and then call 'run' method on that generator, bypassing all
          generator selection.