add an attribute
        
        :parameter dimlist: list of dimensions
        :parameter dimvalues: list of values for dimlist

def add(self,attrlist,attrvalues):
        '''
        add an attribute
        
        :parameter dimlist: list of dimensions
        :parameter dimvalues: list of values for dimlist
        '''
        for i,d in enumerate(attrlist):
            self[d] = attrvalues[i]