File in the following as SystemUser and commit:
category: 'Group Membership'
"Returns all the elements of the receiver that are in the group represented by
aGroupString. If the current session does not have the authorizations required
for this operation, raises an error."
| theGroup |
theGroup := AllGroups _validateGroupString: aGroupString .
^ self select: [:each | (each groups includesIdentical: theGroup)]