Type to be used in Column statements to store python timedeltas.
If it's possible it uses native engine features to store timedeltas (now it's only PostgreSQL Interval type), if there is no such it fallbacks to DateTime storage with converting from/to timedelta on the fly
Converting is very simple - just use epoch(zero timestamp, 01.01.1970) as base, so if we need to store timedelta = 1 day (24 hours) in database it will be stored as DateTime = '2nd Jan 1970 00:00', see bind_processor and result_processor to actual conversion code
Checks if engine has native implementation of timedelta python type, if so it returns right class to handle it, if there is no native support, it fallback to engine's DateTime implementation class
loads the dialect-specific implementation of this type.
by default calls dialect.type_descriptor(self.impl), but can be overridden to provide different behavior.
return a list of classes to test for a match when adapting this type to a dialect-specific type.