public override IEnumerator <KeyValuePair <K, ICollection <V> > > GetEnumerator()
            {
                IPredicate <KeyValuePair <K, ICollection <V> > >  filter1 = null;
                IEnumerator <KeyValuePair <K, ICollection <V> > > iter1   = new FilteredIterator <KeyValuePair <K, ICollection <V> > >(this._enclosing.originalMap.GetEnumerator(), filter1);
                IPredicate <KeyValuePair <K, ICollection <V> > >  filter2 = null;
                IEnumerator <KeyValuePair <K, ICollection <V> > > iter2   = new FilteredIterator <KeyValuePair <K, ICollection <V> > >(this._enclosing.deltaMap.GetEnumerator(), filter2);

                return(new ConcatenationIterator <KeyValuePair <K, ICollection <V> > >(iter1, iter2));
            }
            public override IEnumerator <KeyValuePair <K, V> > GetEnumerator()
            {
                IPredicate <KeyValuePair <K, V> >  filter1 = null;
                IEnumerator <KeyValuePair <K, V> > iter1   = new FilteredIterator <KeyValuePair <K, V> >(this._enclosing.originalMap.GetEnumerator(), filter1);
                IPredicate <KeyValuePair <K, V> >  filter2 = null;
                // end class NullingIterator
                IEnumerator <KeyValuePair <K, V> > iter2 = new FilteredIterator <KeyValuePair <K, V> >(new _T1529859365 <K, V>(this, this._enclosing.deltaMap.GetEnumerator()), filter2);

                return(new ConcatenationIterator <KeyValuePair <K, V> >(iter1, iter2));
            }