Behavior specification - Composition: Consider making the argument-list optional

7.2.2.4.7 Behavior specification: Composition
The composition grammar rule currently reads:
composition ::= composition-operator ['(' argument-list ')']':' NEWLINE INDENT:

Consider making the argument-list optional, since the standard shows cases where empty parentheses are used (see Code 4. Use of the parallel operator), i.e.:
composition ::= composition-operator ['(' [argument-list] ')']':' NEWLINE INDENT