Now I wonder if the new implementation is correct because it would be nice to take into account class definition size.
MooseAbstractGroup >> numberOfLinesOfCode
<MSEProperty: #numberOfLinesOfCode type: #Number>
<MSEComment: 'The number of classes in the model'>
^ self
lookUpPropertyNamed: #numberOfLinesOfCode
computedAs: [ self allMethods sum: #numberOfLinesOfCode ]