code: function checkPath(path) {
      const integerKeySegments =
          path.filter(segment => (/^(0|[1-9][0-9]*)$/.test(segment)));
      if (integerKeySegments.length) {
          warn(`Integer keys will come first in object iteration even if ` +
               `other keys are defined before. Wrap key with '/' to avoid ` +
               `this behavior (${
                  integerKeySegments
                      .map(segment => `"${segment}" => "/${segment}/"`).join(', ')
                }).`);
      }
  }
docs: Doesn't modify passed argument