Support complex types via branches

This commit is a proof of concept update of vss-tools to support
higher order/complex types via a variation of the approach outlined in https://github.com/COVESA/vehicle_signal_specification/wiki/Proposal-%22struct%22:-Just-model-as-branches,-the-rest-is-deployment

Ref: COVESA/vehicle_signal_specification#326

**Description  **
The main idea is that we are trying to model a sensor of Complex type - `ObstacleList` as a branch.
The current limitation with branches is that you cannot have arrays of branches.

With the understanding that branches are to be treated as a data type (like primitive and their array equivalent),
what we need is a way to convey the fact that the branch represents a collection/array.
In the case of primitives, we use the operator `[]` for this purpose. For example, an array type `uint8` is denoted by adding the suffix `[]`.

On a similar path, we can utilize the already available `arraysize` property of a VSS node to specify the array size of a branch typed node.

In this commit, the VSS tools are updated to proceess the `arraysize` key for branch typed nodes.

For reference, the type is defined as follows:
```
ObstacleClass
{
    uint64 class
}

Obstacle
{
    uint64 id
    ObstacleClass class
    float64 probability
}

ObstacleList
{
    Obstacle[] data
}
```

All the relevant files are included in the commit.

vspec -> json: `python vspec2json.py ObstacleArray.vspec --json-pretty out.json`

The resulting JSON output contains the attribute "arraysize" for the branch typed nodes if defined.

Obstacle.vspec

@@ -0,0 +1,11 @@
+Id:
+    type: attribute
+    datatype: int64
+
+Probability:
+    type: attribute
+    datatype: float
+
+ObstacleClass:
+    type: branch
+#include ObstacleClass.vspec ObstacleClass

ObstacleArray.vspec

@@ -0,0 +1,17 @@
+Vehicle:
+    type: branch
+
+Vehicle.ADAS:
+    type: branch
+
+Vehicle.ADAS.Lidar:
+    type: branch
+
+Vehicle.ADAS.Lidar.Front:
+    type: branch
+
+Vehicle.ADAS.Lidar.Front.Obstacles:
+    type: branch
+    arraysize: 10
+
+#include ObstacleData.vspec Vehicle.ADAS.Lidar.Front.Obstacles

ObstacleClass.vspec

@@ -0,0 +1,3 @@
+Class:
+    type: attribute
+    datatype: uint64

ObstacleData.vspec

@@ -0,0 +1,4 @@
+Data:
+    type: branch
+
+#include Obstacle.vspec Data

out.json

@@ -0,0 +1,70 @@
+{
+  "Vehicle": {
+    "children": {
+      "ADAS": {
+        "children": {
+          "Lidar": {
+            "children": {
+              "Front": {
+                "children": {
+                  "Obstacles": {
+                    "arraysize": 10,
+                    "children": {
+                      "Data": {
+                        "children": {
+                          "Id": {
+                            "datatype": "int64",
+                            "description": null,
+                            "type": "attribute",
+                            "uuid": "31f7ac1946da58a194c1c6a8dad9cf1d"
+                          },
+                          "ObstacleClass": {
+                            "children": {
+                              "Class": {
+                                "datatype": "uint64",
+                                "description": null,
+                                "type": "attribute",
+                                "uuid": "c30ce72db64057fd99ac502190bf5fcb"
+                              }
+                            },
+                            "description": null,
+                            "type": "branch",
+                            "uuid": "9ea15f3abd1656e096bcdc5ee6dcbba3"
+                          },
+                          "Probability": {
+                            "datatype": "float",
+                            "description": null,
+                            "type": "attribute",
+                            "uuid": "32e416f193d250d3a5f96f0f4789bee3"
+                          }
+                        },
+                        "description": null,
+                        "type": "branch",
+                        "uuid": "9646d03cc6845c42834aa74fc91a1cfa"
+                      }
+                    },
+                    "description": null,
+                    "type": "branch",
+                    "uuid": "6ae7d48f9cd25ff694dc5ebd02f90522"
+                  }
+                },
+                "description": null,
+                "type": "branch",
+                "uuid": "f96d319c62615760861d8abe645081af"
+              }
+            },
+            "description": null,
+            "type": "branch",
+            "uuid": "aac706a4d4ca599c824ebc479c47540c"
+          }
+        },
+        "description": null,
+        "type": "branch",
+        "uuid": "14c2b2e1297b513197d320a5ce58f42e"
+      }
+    },
+    "description": null,
+    "type": "branch",
+    "uuid": "ccc825f94139544dbb5f4bfd033bece6"
+  }
+}

vspec/model/vsstree.py

@@ -113,6 +113,9 @@ def __init__(self, name, source_dict: dict, parent=None, children=None, break_on
         if "instances" in source_dict.keys():
             self.instances = source_dict["instances"]
 
+        if "arraysize" in source_dict.keys():
+            self.arraysize = source_dict["arraysize"]
+
         if "deprecation" in source_dict.keys():
             self.deprecation = source_dict["deprecation"]
 

vssexporters/vss2json.py

@@ -37,6 +37,8 @@ def export_node(json_dict, node, generate_uuid):
         json_dict[node.name]["default"] = node.default_value
     if node.deprecation != "":
         json_dict[node.name]["deprecation"] = node.deprecation
+    if hasattr(node, 'arraysize'):
+        json_dict[node.name]["arraysize"] = node.arraysize
 
     # in case of unit or aggregate, the attribute will be missing
     try: