Get a socket from the pool. Use with a "with" statement.

        Returns a :class:`SocketInfo` object wrapping a connected
        :class:`socket.socket`.

        This method should always be used in a with-statement::

            with pool.get_socket(credentials, checkout) as socket_info:
                socket_info.send_message(msg)
                data = socket_info.receive_message(op_code, request_id)

        The socket is logged in or out as needed to match ``all_credentials``
        using the correct authentication mechanism for the server's wire
        protocol version.

        Can raise ConnectionFailure or OperationFailure.

        :Parameters:
          - `all_credentials`: dict, maps auth source to MongoCredential.
          - `checkout` (optional): keep socket checked out.

def get_socket(self, all_credentials, checkout=False):
        """Get a socket from the pool. Use with a "with" statement.

        Returns a :class:`SocketInfo` object wrapping a connected
        :class:`socket.socket`.

        This method should always be used in a with-statement::

            with pool.get_socket(credentials, checkout) as socket_info:
                socket_info.send_message(msg)
                data = socket_info.receive_message(op_code, request_id)

        The socket is logged in or out as needed to match ``all_credentials``
        using the correct authentication mechanism for the server's wire
        protocol version.

        Can raise ConnectionFailure or OperationFailure.

        :Parameters:
          - `all_credentials`: dict, maps auth source to MongoCredential.
          - `checkout` (optional): keep socket checked out.
        """
        # First get a socket, then attempt authentication. Simplifies
        # semaphore management in the face of network errors during auth.
        sock_info = self._get_socket_no_auth()
        try:
            sock_info.check_auth(all_credentials)
            yield sock_info
        except:
            # Exception in caller. Decrement semaphore.
            self.return_socket(sock_info)
            raise
        else:
            if not checkout:
                self.return_socket(sock_info)