def METHOD_NAME(self, expression, qualifier=None) -> str:
    if isinstance(expression, ComparisonExpression):  # Base Case
        # Resolve STIX Object Path to a field in the target Data Model
        stix_object, stix_field = expression.object_path.split(':')
        comparator = self.comparator_lookup[expression.comparator]
        if expression.negated:
            comparator = 'NOT ' + comparator
        if qualifier is not None:
            self._convert_qualifier_times_to_unix_times(qualifier)
        if (expression.comparator == ComparisonComparators.In and isinstance(expression.value, SetValue)):
            expression.value = list(expression.value.element_iterator())
        self.parsed_pattern.append({'attribute': expression.object_path, 'comparison_operator': comparator, 'value': expression.value})
    elif isinstance(expression, CombinedComparisonExpression):
        if qualifier is not None:
            self._convert_qualifier_times_to_unix_times(qualifier)
        self.METHOD_NAME(expression.expr1)
        self.METHOD_NAME(expression.expr2)
    elif isinstance(expression, ObservationExpression):
        self.METHOD_NAME(expression.comparison_expression, qualifier)
    elif hasattr(expression, 'qualifier') and hasattr(expression, 'observation_expression'):
        if isinstance(expression.observation_expression, CombinedObservationExpression):
            self.METHOD_NAME(expression.observation_expression.expr1)
            self.METHOD_NAME(expression.observation_expression.expr2, expression.qualifier)
        else:
            self.METHOD_NAME(expression.observation_expression.comparison_expression, expression.qualifier)
    elif isinstance(expression, CombinedObservationExpression):
        self.METHOD_NAME(expression.expr1)
        self.METHOD_NAME(expression.expr2)
    elif isinstance(expression, Pattern):
        self.METHOD_NAME(expression.expression)
    else:
        raise RuntimeError("Unknown Recursion Case for expression={}, type(expression)={}".format(
            expression, type(expression)))