def installNameResolver(resolver):
        """
        Set the internal resolver to use for name lookups.

        @type resolver: An object providing the L{IHostnameResolver} interface.
        @param resolver: The new resolver to use.

        @return: The previously installed resolver.
        @rtype: L{IHostnameResolver}
        """

        Set the internal resolver to use for name lookups.

        @type resolver: An object providing the L{IHostnameResolver} interface.
        @param resolver: The new resolver to use.

        @return: The previously installed resolver.
        @rtype: L{IHostnameResolver}
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/interfaces.py