def set_active_range(self, i1, i2):
logger.debug("<STR_LIT>", (i1, i2))<EOL>self._active_fraction = (i2 - i1) / float(self.length_original())<EOL>self._index_start = i1<EOL>self._index_end = i2<EOL>self.select(None)<EOL>self.set_current_row(None)<EOL>self._length_unfiltered = i2 - i1<EOL>self.signal_active_fraction_changed.emit(self, self._active_fraction)<EOL>
Sets the active_fraction, set picked row to None, and remove selection.

        TODO: we may be able to keep the selection, if we keep the expression, and also the picked row