Initialize a MessageContext object from a json dictionary.

def _from_dict(cls, _dict):
        """Initialize a MessageContext object from a json dictionary."""
        args = {}
        if 'global' in _dict:
            args['global_'] = MessageContextGlobal._from_dict(
                _dict.get('global'))
        if 'skills' in _dict:
            args['skills'] = MessageContextSkills._from_dict(
                _dict.get('skills'))
        return cls(**args)