protected SystemMember removeSystemMember(SystemMember systemMember) {
    return removeSystemMember(((SystemMemberImpl) systemMember).getInternalId());
  }
Removes a SystemMember from this system's list of known members.

@param systemMember the member to remove
@return the system member that was removed; null if no match was found
geode-core/src/main/java/org/apache/geode/admin/internal/AdminDistributedSystemImpl.java