def disconnect(self, conn):
        """
        Disconnect a database connection associated with this pool.

        Note: This function should only be used by the same thread which called
        L{ConnectionPool.connect}. As with C{connect}, this function is not
        used in normal non-threaded Twisted code.
        """
        tid = self.threadID()
        if conn is not self.connections.get(tid):
            raise Exception("wrong connection for thread")
        if conn is not None:
            self._close(conn)
            del self.connections[tid]

        Disconnect a database connection associated with this pool.

        Note: This function should only be used by the same thread which called
        L{ConnectionPool.connect}. As with C{connect}, this function is not
        used in normal non-threaded Twisted code.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/enterprise/adbapi.py