issue with netcdf file export when using seed_cone with specified z, or other property, as array rather than single value

[simonweppe]

Hi all,

If one specifies an array rather than single value for one of the properties when seeding particle using seed_cone(), it seems that the netcdf export will fail because a "ndarray is not JSON serializable".

A fix could be to convert any properties that is an array to a string before saving to self.seed_geojson ? Not too sure what's a good practice for json in that context ?

For example below , included line 1638 of basemodel.py. Happy to make a pull request if that's acceptable.

for key in properties.keys():
    if isinstance(properties[key],np.ndarray):
        properties[key] = np.array2string(properties[key])