Initialization of self.self_weight Leads to Empty JSON input and Error

[Jeroen124]

Problemn

When a model is created, an empty self.self_weight model is assigned to the Model, which results in an erroneous JSON output and subsequent error.

model.py

class Model:

    def __init__(self, unit_system: Literal["metric", "imperial"], vertical_axis: Literal["Y", "Z"] = 'Y'):
        """Create an s3d_model object.

        Args:
            unit_system (str): {'metric' | 'imperial'}
            vertical_axis (str, optional): {"Y" | "Z"}. Defaults to 'Y'.

        Example: 
            Default for: metric | imperial::
            {
                "length": "m" | 'ft',
                 "section_length": "mm" | 'in',
                 "material_strength": "mpa" | 'ksi',
                 "density": "kg/m3" | 'lb/ft3',
                 "force": "kn" | 'kip',
                 "moment": "kn-m" | 'kip-ft',
                 "pressure": "kpa" | 'ksf',
                 "mass": "kg" | 'kip',
                 "translation": "mm" | 'in',
                 "stress": "mpa" | 'ksi'
            }
        """
        self.settings = Settings(unit_system, vertical_axis)
        self.nodes = Nodes()
        self.members = Members()
        self.plates = Plates()
        self.meshed_plates = MeshedPlates()
        self.sections = Sections()
        self.materials = Materials()
        self.supports = Supports()
        self.settlements = Settlements()
        self.point_loads = PointLoads()
        self.moments = Moments()
        self.distributed_loads = DistributedLoads()
        self.pressures = Pressures()
        self.area_loads = AreaLoads()
        self.member_prestress_loads = {}
        self.self_weight = SelfWeights()
        self.load_combinations = LoadCombinations()
        self.load_cases = {}
        self.nodal_masses = {}
        self.nodal_masses_conversion_map = {}
        self.spectral_loads = {}
        self.groups = []

This results in a json with an empty self_weight:
"self_weight": {},

This in turn results in the following error:
{"response": {"status": 1, "msg": "The function 'S3D.model.set' could not be completed for an unknown reason. Check screenshot for more information.",

Possible solution:

Initializing self.self_weight as an empty dictionary might be sufficient:

Initializing the self.load_combinations = {}
However, the implications of this change are not fully understood and require further investigation to ensure it does not introduce other issues.