ARCSpecies does not show atom labels for the mol object if it was generated from a `species_dict`

[kfir4444]

Describe the bug ARCSpecies does not show atom labels for the mol object if it was generated from a species_dict

How to reproduce

>>> from arc.species import ARCSpecies
>>> spc = ARCSpecies(label="fail", smiles="CC")
>>> for index, atom in enumerate(spc.mol.atoms):
...     atom.label = str(index)
... 
>>> new_spc = ARCSpecies(species_dict=spc.as_dict())
>>> print([atom.label for atom in new_spc.mol.atoms])
['', '', '', '', '', '', '', '']

even though the species_dict does have atom labels:

'mol': {'atoms': [{'element': {'number': 6, 'isotope': -1},
    'radical_electrons': 0,
    'charge': 0,
    'label': '0',
    'lone_pairs': 0,
    'id': -27544,
    'props': {'inRing': False},
    'atomtype': 'Cs',
    'edges': {-27543: 1.0, -27542: 1.0, -27541: 1.0, -27540: 1.0}},
   {'element': {'number': 6, 'isotope': -1},
    'radical_electrons': 0,
    'charge': 0,
    'label': '1',
    'lone_pairs': 0,
    'id': -27543,
    'props': {'inRing': False},
    'atomtype': 'Cs',
    'edges': {-27544: 1.0, -27539: 1.0, -27538: 1.0, -27537: 1.0}},
   {'element': {'number': 1, 'isotope': -1},
    'radical_electrons': 0,
    'charge': 0,
    'label': '2',
    'lone_pairs': 0,
    'id': -27542,
    'props': {'inRing': False},
    'atomtype': 'H',
    'edges': {-27544: 1.0}},
   {'element': {'number': 1, 'isotope': -1},
    'radical_electrons': 0,
    'charge': 0,
    'label': '3',
    'lone_pairs': 0,
    'id': -27541,
    'props': {'inRing': False},
    'atomtype': 'H',
    'edges': {-27544: 1.0}},
   {'element': {'number': 1, 'isotope': -1},
    'radical_electrons': 0,
    'charge': 0,
    'label': '4',
    'lone_pairs': 0,
    'id': -27540,
    'props': {'inRing': False},
    'atomtype': 'H',
    'edges': {-27544: 1.0}},
   {'element': {'number': 1, 'isotope': -1},
    'radical_electrons': 0,
    'charge': 0,
    'label': '5',
    'lone_pairs': 0,
    'id': -27539,
    'props': {'inRing': False},
    'atomtype': 'H',
    'edges': {-27543: 1.0}},
   {'element': {'number': 1, 'isotope': -1},
    'radical_electrons': 0,
    'charge': 0,
    'label': '6',
    'lone_pairs': 0,
    'id': -27538,
    'props': {'inRing': False},
    'atomtype': 'H',
    'edges': {-27543: 1.0}},
   {'element': {'number': 1, 'isotope': -1},
    'radical_electrons': 0,
    'charge': 0,
    'label': '7',
    'lone_pairs': 0,
    'id': -27537,
    'props': {'inRing': False},
    'atomtype': 'H',
    'edges': {-27543: 1.0}}],

(see the 'labels' on the atom list) Expected behavior return the same labels.

Additional context Accurate parsing of the species object is important for restarts and for testing, as they help to avoid obsolete callings of other functions while performing tests, which may cause unrelated failures. :smile: