def project_interval_backward(self, c_interval):
return self.src_tm.g_to_c(self.dst_tm.c_to_g(c_interval))<EOL>
project c_interval on the destination transcript to the
source transcript

:param c_interval: an :class:`hgvs.interval.Interval` object on the destination transcript
:returns: c_interval: an :class:`hgvs.interval.Interval` object on the source transcript