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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 manual_close(self):
 """ Close the underlying connection without returning it to the pool. """

        if self.is_closed():
            return False

        # Obtain reference to the connection in-use by the calling thread.
        conn = self.connection()

        # A connection will only be re-added to the available list if it is
        # marked as "in use" at the time it is closed. We will explicitly
        # remove it from the "in use" list, call "close()" for the
        # side-effects, and then explicitly close the connection.
        self._in_use.pop(self.conn_key(conn), None)
        self.close()
        self._close(conn, close_conn=True)