def add_interval(self,istart,iend,index):
        self.intervals.append([istart,iend,index])
        self.points.append(istart)
        self.points.append(iend)
adds an interval to the class
dataset/ETHPy150Open fp7-ofelia/ocf/optin_manager/src/python/openflow/optin_manager/flowspace/helper.py/Intervals.add_interval