code: function checkPseudoClass2(i) {
    const start = i;
    let l;
  
    // Skip `:`.
    i++;
  
    if (i >= tokensLength) return 0;
  
    if (l = checkIdentOrInterpolation(i)) i += l;
    else return 0;
  
    if (i >= tokensLength ||
        tokens[i].type !== TokenType.LeftParenthesis) return 0;
  
    const right = tokens[i].right;
  
    // Skip `(`.
    i++;
  
    if (l = checkSC(i)) i += l;
  
    if (l = checkIdentOrInterpolation(i)) i += l;
    else return 0;
  
    if (l = checkSC(i)) i += l;
  
    if (i !== right) return 0;
  
    // Skip `)`.
    i++;
  
    return i - start;
  }
docs: (1) `:nth-child(odd)`
  (2) `:nth-child(even)`
  (3) `:lang(de-DE)`