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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 add_source_override(self, fullname, path, source, is_pkg):
 """ Explicitly install a source cache entry, preventing usual lookup methods from being used. Beware the value of `path` is critical when `is_pkg` is specified, since it directs where submodules are searched for. :param str fullname: Name of the module to override. :param str path: Module's path as it will appear in the cache. :param bytes source: Module source code as a bytestring. :param bool is_pkg: :data:`True` if the module is a package. """

        self._found_cache[fullname] = (path, source, is_pkg)