Shopify GraphQL collection query with product metafield

collectionByHandle.graphql

query productCollection($handle: String!, $firstProducts: Int!, $metafield: String!) {
  collectionByHandle(handle: $handle) {
    id
    title
    productsCount {
      count
    }
    products(first: $firstProducts) {
      edges {
        node {
          title
          handle
          seo {
            title
            description
          }
          metafields(first: 1, keys: [$metafield]) {
            edges {
              node {
                key
                value
              }
            }
          }
        }
      }
    }
  }
}