Patrick Rein uploaded a new version of Collections to project The Trunk:
http://source.squeak.org/trunk/Collections-pre.822.mcz

==================== Summary ====================

Name: Collections-pre.822
Author: pre
Time: 20 March 2019, 8:05:20.383677 pm
UUID: 483c4461-cee4-4a4f-82d3-fbc03e7201cc
Ancestors: Collections-dtl.821

Adds #isMutator to Symbol which is analogous to asMutator.

=============== Diff against Collections-dtl.821 ===============

Item was added:
+ ----- Method: Symbol>>isMutator (in category 'testing') -----
+ isMutator
+ 
+ 	^ self isKeyword and: [self numArgs = 1]!