function parseSingleQuotesString(state) {
    var node, str;

    if (state.token === '\'') {
      str = parseSingleQuotesStringToken(state); // create constant

      node = new ConstantNode(str); // parse index parameters

      node = parseAccessors(state, node);
      return node;
    }

    return parseMatrix(state);
  }
Parse a single quotes string.
@return {Node} node
@private