code: public Set<Terminal> get(Construction construction) {
  	if (construction.isTerminal()) {
  	    Set<Terminal> result = new LinkedHashSet<Terminal>();
  	    result.add((Terminal) construction);
  	    return result;
  	}
  	return firstGrammar.get(construction.getName());
      }
docs: This method returns the first set for a specified construction.
  
  This method contains rule 1 from Dragon Book:
  
  1) Wenn X ein Terminal ist, ist FIRST(X) = (X).
  
  @param construction
  is the construction to get the firsts from.
  @return A {@link Set} of {@link Terminal}s is returned.