Check people picker value is user or group or both

Hi,

In CSOM .Net we are getting people picker value as FieldUserValue. We want to check whether the value is user or group.

How can we do it. "PrimaryLead" is a list column which accepts user or group.

primary=(FieldUserValue)listItems[0]["PrimaryLead"];
// How to check primary is user or group. if it is group we need to get users in it.