@property<EOL><INDENT>def isnap(self):<DEDENT>
if self._isnap is UNDETERMINED:<EOL><INDENT>istep = None<EOL>isnap = -<NUM_LIT:1><EOL>while (istep is None or istep < self.istep) and isnap < <NUM_LIT>:<EOL><INDENT>isnap += <NUM_LIT:1><EOL>istep = self.sdat.snaps[isnap].istep<EOL>self.sdat.snaps.bind(isnap, istep)<EOL><DEDENT>if istep != self.istep:<EOL><INDENT>self._isnap = None<EOL><DEDENT><DEDENT>return self._isnap<EOL>
Snapshot index corresponding to time step.

        It is set to None if no snapshot exists for the time step.