Branch, repeat, and condition queries

read_batch()
    .var_as(
        "user",
        g().n_with_label("User")
            .where_(Predicate::eq("username", "alice")),
    )
    .var_as_if(
        "posts",
        BatchCondition::VarNotEmpty("user".to_string()),
        g().n(NodeRef::var("user"))
            .out(Some("AUTHORED"))
            .value_map(Some(vec!["$id", "title"])),
    )
    .returning(["posts"]);

readBatch()
  .varAs("user", g().nWithLabel("User").where(Predicate.eq("username", "alice")))
  .varAsIf(
    "posts",
    BatchCondition.varNotEmpty("user"),
    g().n(NodeRef.var("user")).out("AUTHORED").valueMap(["$id", "title"]),
  )
  .returning(["posts"]);

helix.ReadQuery("user_posts").
	VarAs("user", helix.G().NWithLabel("User").Where(helix.PredEq("username", "alice"))).
	VarAsIf(
		"posts",
		helix.VarNotEmpty("user"),
		helix.G().N(helix.NodeVar("user")).Out("AUTHORED").ValueMap("$id", "title"),
	).
	Returning("posts")

(
    read_batch()
    .var_as(
        "user",
        g().n_with_label("User").where(Predicate.eq("username", "alice")),
    )
    .var_as_if(
        "posts",
        BatchCondition.var_not_empty("user"),
        g().n(NodeRef.var("user")).out("AUTHORED").value_map(["$id", "title"]),
    )
    .returning(["posts"])
)

{
  "request_type": "read",
  "query_name": "user_posts",
  "query": {
    "read": {
      "entries": [
        {
          "query": {
            "name": "user",
            "root": {
              "where": {
                "input": {
                  "nodes_where": {
                    "predicate": {
                      "eq": {
                        "left": { "property": "$label" },
                        "right": { "constant": { "string": "User" } }
                      }
                    }
                  }
                },
                "predicate": {
                  "eq": {
                    "left": { "property": "username" },
                    "right": { "constant": { "string": "alice" } }
                  }
                }
              }
            }
          }
        },
        {
          "query": {
            "name": "posts",
            "root": {
              "value_map": {
                "input": {
                  "out": {
                    "input": { "nodes": { "reference": { "var": "user" } } },
                    "label": "AUTHORED"
                  }
                },
                "properties": ["$id", "title"]
              }
            },
            "condition": { "var_not_empty": "user" }
          }
        }
      ],
      "returns": ["posts"]
    }
  }
}

MATCH (user:User)
WHERE user.username = 'alice'
MATCH (user)-[:AUTHORED]->(post)
RETURN id(post) AS id, post.title AS title