code: private boolean isReservedKeyword() {
  
          final String content = mToken.getContent();
          return isKindTest() || "item".equals(content) || "if".equals(content)
              || "empty-sequence".equals(content) || "typeswitch".equals(content);
      }
docs: Although XPath is supposed to have no reserved words, some keywords are
  not allowed as function names in an unprefixed form because expression
  syntax takes precedence.
  
  @return true if the token is one of the reserved words of XPath 2.0