public SyntacticCategory addArgument(SyntacticCategory argument, Direction direction) {
    return SyntacticCategory.createFunctional(direction, this, argument);
  }
public SyntacticCategory addArgument ( SyntacticCategory argument , Direction direction ) { return SyntacticCategory . createFunctional ( direction , this , argument ) ; }
Gets the syntactic category which accepts {@code argument} in
{@code direction} and returns {@code this}.

@param argument
@param direction
@return