Return a list of dates from the list between <fromdate> and <todate>
        (inclusive)

def subset(self, fromdate, todate):
        '''
        Return a list of dates from the list between <fromdate> and <todate>
        (inclusive)
        '''
#CONSIDER: raise an exception if a date is not in self
        i_from = self.index(fromdate)
        if fromdate != self[i_from]:
            # don't go back before fromdate
            i_from += 1
        i_to = self.index(todate)
        return self[i_from:i_to + 1]