Loads a single fixture.

        Args:
            * fixture_id (str): the id of the fixture
            * head2head (int, optional): load the previous n fixture of the two teams

        Returns:
            * :obj: json: the fixture-json

def get_fixture(self, fixture_id, head2head=None):
        """
        Loads a single fixture.

        Args:
            * fixture_id (str): the id of the fixture
            * head2head (int, optional): load the previous n fixture of the two teams

        Returns:
            * :obj: json: the fixture-json
        """
        filters = []
        if head2head is not None and int(head2head) > 0:
            self.logger.debug(f'Getting fixture {fixture_id}. head2head is {head2head}.')
            filters.append(self.__createFilter('head2head', head2head))
        else:
            self.logger.debug(f'Getting fixture {fixture_id}.')

        return self._request('fixtures', fixture_id, filters=filters)