Right now, the code at line 205 is "for nothing" -- this code always overrides the value calculated there -- It would be simpler to move this code into that function. Since the result that you will return from that function to the head of this loop will be a string, you can leave out:

    i = u"'%s'" % (i)

there and completely remove the

	    elif self.__type == "timestamp":

block to allow the timestamp cases to pass into the next block -- elif isinstance(i, basestring):

In summary, this code will work correctly as it is, but it could be made simpler.
Please push another commit to this branch with these suggested changes -- and maybe eliminating the IS_VOLT flag at the same time?