code: public VariableRef[] getVariableRefs() {
          Collection<VariableRef> allRefs = new ArrayList<VariableRef>();
          fillVariableRefs(allRefs, this);
          return allRefs.toArray(new VariableRef[allRefs.size()]);
      }
docs: Returns all the variable references made from this scope and all child
  scopes.
  
  @return non-null array of VariableRefs.