Validate the provided kwargs and return options as json string.

def parse_options(self, kwargs):
        """Validate the provided kwargs and return options as json string."""
        kwargs = {camelize(key): value for key, value in kwargs.items()}
        for key in kwargs.keys():
            assert key in self.valid_options, (
                'The option {} is not in the available options: {}.'
                .format(key, ', '.join(self.valid_options))
            )
            assert isinstance(kwargs[key], self.valid_options[key]), (
                'The option {} must be one of the following types: {}.'
                .format(key, self.valid_options[key])
            )
        return kwargs