Initialize a ClassificationCollection object from a json dictionary.

def _from_dict(cls, _dict):
        """Initialize a ClassificationCollection object from a json dictionary."""
        args = {}
        if 'classifier_id' in _dict:
            args['classifier_id'] = _dict.get('classifier_id')
        if 'url' in _dict:
            args['url'] = _dict.get('url')
        if 'collection' in _dict:
            args['collection'] = [
                CollectionItem._from_dict(x) for x in (_dict.get('collection'))
            ]
        return cls(**args)