How to implement logic when serializing nodes for gatsby-plugin-advanced-sitemap?

Developer help
1

Hi,
I am using gatsby-plugin-advanced-sitemap to generate an advanced sitemap.

What I would like to achieve is implement logic for generating the sitemaps using the data fetched from Graphql queries and passed to a function that in the end should result with this:

{
  **pages**: [{url: '/test/', lastmod: 'YYYY-MM-DD', ...not how to pass all required fields to satisfy the expected result bellow}],
 partnerships: [{url: /partnerhips/partner, lastmod: 'YYYY-MM-DD}]
}

So this will generate categorised sitemaps

In the end I would like to have these fields for each sitemap entity

<url>
        <loc>https://${host}${route}</loc>
        <lastmod>${date}</lastmod>
         <link
               rel="alternate"
               hreflang="mk"
               href="https://${host}${route}"
               />
        <link
               rel="alternate"
               hreflang="en"
               href="https://${host}/en${route}"
       />
     </url>
     <url>
        <loc>https://${host}/en${route}</loc>
        <lastmod>${date}</lastmod>
           <link
               rel="alternate"
               hreflang="mk"
               href="https://${host}${route}"
               />
       <link
               rel="alternate"
               hreflang="en"
               href="https://${host}/en${route}"
       />
     </url>

This is how the plugin is set in gatsby-config.js:

const { GetSiteMap } = require("./src/lib/services/sitemap.service");

{
      resolve: "gatsby-plugin-advanced-sitemap",
      options: {
        query: `{
          allSanityPages {
            edges {
              node {
                _updatedAt
                slugs {
                  slug_ch {
                    current
                  }
                  slug_en {
                    current
                  }
                  slug_gr {
                    current
                  }
                  slug_se {
                    current
                  }
                }
              }
            }
          }
          allSanityDomains {
            edges {
              node {
                _updatedAt
              
              }
            }
          }
          allSanityPartnerships {
            edges {
              node {
                _updatedAt
                slugs {
                  slug_ch {
                    current
                  }
                  slug_en {
                    current
                  }
                  slug_gr {
                    current
                  }
                  slug_se {
                    current
                  }
                }
                localeAvailability {
                  ch
                  gr
                  se
                }
              }
            }
          }
      }`,
        serializer: (data) => GetSiteMap(data, process.env.GATSBY_LANG),
      },
    },

and GetSiteMap function (initial version just to try) :

function GetSiteMap(data, lang) {
  console.log(Object.keys(data));
  let sitemap = {};
  const domains = MapEdgesToNodes(data.allSanityDomains);
  const pages = MapEdgesToNodes(data.allSanityPages);
  const partnerships = MapEdgesToNodes(data.allSanityPartnerships);

  const partnersPage = GetCurrentPage("partners", pages);
  if (
    partnerships &&
    partnerships.length > 0 &&
    partnersPage &&
    partnersPage.slugs &&
    partnersPage.slugs[`slug_${lang}`] &&
    partnersPage.slugs[`slug_${lang}`].current
  ) {
    console.log("CREATING SITEMAP");
    sitemap["partnerships"] = partnerships.map((p) => {
      return {
        node: {
          url:
            partnersPage.slugs[`slug_${lang}`].current +
            "/" +
            p.slugs[`slug_${lang}`].current +
            "/",
        },
      };
    });
  }
  return sitemap;
}

Anyways I always get:

Cannot read property 'replace' of undefined

  233 |
  234 |             var sourceType = node.__typename ? "all" + node.__typename : source;
> 235 |             var slug = sourceType === "allMarkdownRemark" || sourceType === "allMdx" || node !== null && node !== void 0 && (_node$fields = node.fields) !== null && _node$fields !== void 0 &&
_node$fields.slug ? node.fields.slug.replace(/^\/|\/$/, "") : node.slug.replace(/^\/|\/$/, "");

It is really important to achieve categorised sitemap and alternative links (for other locales) for each entity