Provides a thread-local transactional wrapper around the root Engine class.
The threadlocal module is invoked when using the strategy="threadlocal" flag with create_engine(). This module is semi-private and is invoked automatically when the threadlocal engine strategy is used.
An Engine that includes support for thread-local managed transactions.
The TLEngine relies upon its Pool having "threadlocal" behavior, so that once a connection is checked out for the current thread, you get that same connection repeatedly.