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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def overlay(self, block_start_string=missing, block_end_string=missing, variable_start_string=missing, variable_end_string=missing, comment_start_string=missing, comment_end_string=missing, line_statement_prefix=missing, line_comment_prefix=missing, trim_blocks=missing, lstrip_blocks=missing, extensions=missing, optimized=missing, undefined=missing, finalize=missing, autoescape=missing, loader=missing, cache_size=missing, auto_reload=missing, bytecode_cache=missing):
 """Create a new overlay environment that shares all the data with the current environment except for cache and the overridden attributes. Extensions cannot be removed for an overlayed environment. An overlayed environment automatically gets all the extensions of the environment it is linked to plus optional extra extensions. Creating overlays should happen after the initial environment was set up completely. Not all attributes are truly linked, some are just copied over so modifications on the original environment may not shine through. """

        args = dict(locals())
        del args['self'], args['cache_size'], args['extensions']

        rv = object.__new__(self.__class__)
        rv.__dict__.update(self.__dict__)
        rv.overlayed = True
        rv.linked_to = self

        for key, value in iteritems(args):
            if value is not missing:
                setattr(rv, key, value)

        if cache_size is not missing:
            rv.cache = create_cache(cache_size)
        else:
            rv.cache = copy_cache(self.cache)

        rv.extensions = {}
        for key, value in iteritems(self.extensions):
            rv.extensions[key] = value.bind(rv)
        if extensions is not missing:
            rv.extensions.update(load_extensions(rv, extensions))

        return _environment_sanity_check(rv)