code: function checkMixin(i) {
    let l;
  
    if (i >= tokensLength) return 0;
  
    if (l = checkMixin1(i)) tokens[i].mixin_type = 1;
    else if (l = checkMixin2(i)) tokens[i].mixin_type = 2;
    else return 0;
  
    return l;
  }
docs: Check if token is part of a LESS mixin
  @param {Number} i Token's index number
  @returns {Number} Length of the mixin