docs: private String getNarrowestScope(FacesContext facesContext, String valueExpression)
      {
          List<String> expressions = extractExpressions(valueExpression);
          // exclude NONE scope, if there are more than one ValueExpressions (see Spec for details)
          String narrowestScope = expressions.size() == 1 ? NONE : APPLICATION;
          boolean scopeFound = false;
          
          for (String expression : expressions)
          {
              String valueScope = getScope(facesContext, expression);
              if (valueScope == null)
              {
                  continue;
              }
              // we have found at least one valid scope at this point
              scopeFound = true;
              if (SCOPE_COMPARATOR.compare(valueScope, narrowestScope) < 0)
              {
                  narrowestScope = valueScope;
              }
          }
          
          return scopeFound ? narrowestScope : null;
      }