def begin(transactionid=None):
if not transactionid:<EOL><INDENT>transactionid = uuid.uuid4()<EOL><DEDENT>return "<STR_LIT>" % transactionid<EOL>
STOMP begin command.

    Start a transaction...

    transactionid:
        This is the id that all actions in this transaction
        will have. If this is not given then a random UUID
        will be generated for this.