def parse_rules(self, tokens, context):
        rules = []
        errors = []
        tokens = iter(tokens)
        for token in tokens:
            if token.type not in ('S', 'CDO', 'CDC'):
                try:
                    if token.type == 'ATKEYWORD':
                        rule = self.read_at_rule(token, tokens)
                        result = self.parse_at_rule(
                            rule, rules, errors, context)
                        rules.append(result)
                    else:
                        rule, rule_errors = self.parse_ruleset(token, tokens)
                        rules.append(rule)
                        errors.extend(rule_errors)
                except ParseError as exc:
                    errors.append(exc)
                    # Skip the entire rule
        return rules, errors
Convert a coordinate string like 'B12' to a tuple ('B', 12)
dataset/ETHPy150Open FichteFoll/CSScheme/tinycsscheme/tinycss/css21.py/CSS21Parser.parse_rules--crossover with--dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/tablib-0.10.0/tablib/packages/openpyxl/cell.py/coordinate_from_string