src/language-yaml/print/flow-mapping-sequence.js/printChildren
function printChildren(path, print, options) {
  const node = path.getValue();
  const parts = path.map(
    (childPath, index) => [
      print(),
      index === node.children.length - 1
        ? ""
        : [
            ",",
            line,
            node.children[index].position.start.line !==
            node.children[index + 1].position.start.line
              ? printNextEmptyLine(childPath, options.originalText)
              : "",
          ],
    ],
    "children"
  );
  return parts;
}