code: function handleExprList (node, options) {
    const values = node.value.map((valueNode) => traverse(valueNode, options)).join(',')
    return `(${values})`
  }
docs: Convert an expression list node to its string representation.
  @param  {object} node    AST expression list node
  @param  {object} options winnow options
  @return {string}         expression list string