public async Task<Dictionary<string, IList<string>>> ReadStringMultimapAsync()
{
ushort len = await ReadShortAsync().AutoConfigureAwait();
var data = new Dictionary<string, IList<string>>(len);
for(int i = 0; i < len; ++i)
{
string key = await ReadStringAsync().AutoConfigureAwait();
IList<string> value = await ReadStringListAsync().AutoConfigureAwait();
data.Add(key, value);
}
return data;
}