How to use the waitress.utilities.build_http_date function in waitress

if not self.close_on_finish:
                    close_on_finish()

            # under HTTP 1.1 keep-alive is default, no need to set the header
        else:
            raise AssertionError('neither HTTP/1.0 or HTTP/1.1')

        # Set the Server and Date field, if not yet specified. This is needed
        # if the server is used as a proxy.
        ident = self.channel.server.adj.ident
        if not server_header:
            response_headers.append(('Server', ident))
        else:
            response_headers.append(('Via', ident))
        if not date_header:
            response_headers.append(('Date', build_http_date(self.start_time)))

        first_line = 'HTTP/%s %s' % (self.version, self.status)
        # NB: sorting headers needs to preserve same-named-header order
        # as per RFC 2616 section 4.2; thus the key=lambda x: x[0] here;
        # rely on stable sort to keep relative position of same-named headers
        next_lines = ['%s: %s' % hv for hv in sorted(
                self.response_headers, key=lambda x: x[0])]
        lines = [first_line] + next_lines
        res = '%s\r\n\r\n' % '\r\n'.join(lines)
        return tobytes(res)

if not self.close_on_finish:
                    close_on_finish()

            # under HTTP 1.1 keep-alive is default, no need to set the header
        else:
            raise AssertionError('neither HTTP/1.0 or HTTP/1.1')

        # Set the Server and Date field, if not yet specified. This is needed
        # if the server is used as a proxy.
        ident = self.channel.server.adj.ident
        if not server_header:
            response_headers.append(('Server', ident))
        else:
            response_headers.append(('Via', ident))
        if not date_header:
            response_headers.append(('Date', build_http_date(self.start_time)))

        first_line = 'HTTP/%s %s' % (self.version, self.status)
        # NB: sorting headers needs to preserve same-named-header order
        # as per RFC 2616 section 4.2; thus the key=lambda x: x[0] here;
        # rely on stable sort to keep relative position of same-named headers
        next_lines = ['%s: %s' % hv for hv in sorted(
                self.response_headers, key=lambda x: x[0])]
        lines = [first_line] + next_lines
        res = '%s\r\n\r\n' % '\r\n'.join(lines)
        return tobytes(res)