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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def parse_condition( cond, selectable, aggregated=False, default_aggregation='sum' ):
 """Create a SQLAlchemy clause from a condition."""

    if cond is None:
        return None

    else:
        if 'and' in cond:
            conditions = [
                parse_condition(
                    c, selectable, aggregated, default_aggregation
                ) for c in cond['and']
            ]
            return and_(*conditions)
        elif 'or' in cond:
            conditions = [
                parse_condition(
                    c, selectable, aggregated, default_aggregation
                ) for c in cond['or']
            ]
            return or_(*conditions)
        elif 'field' not in cond:
            raise BadIngredient('field must be defined in condition')
        field = parse_field(
            cond['field'],
            selectable,
            aggregated=aggregated,
            default_aggregation=default_aggregation
        )
        if 'in' in cond:
            value = cond['in']
            if isinstance(value, dict):
                raise BadIngredient('value for in must be a list')
            condition_expression = getattr(field, 'in_')(tuple(value))
        elif 'gt' in cond:
            value = cond['gt']
            if isinstance(value, (list, dict)):
                raise BadIngredient('conditional value must be a scalar')
            condition_expression = getattr(field, '__gt__')(value)
        elif 'gte' in cond:
            value = cond['gte']
            if isinstance(value, (list, dict)):
                raise BadIngredient('conditional value must be a scalar')
            condition_expression = getattr(field, '__ge__')(value)
        elif 'lt' in cond:
            value = cond['lt']
            if isinstance(value, (list, dict)):
                raise BadIngredient('conditional value must be a scalar')
            condition_expression = getattr(field, '__lt__')(value)
        elif 'lte' in cond:
            value = cond['lte']
            if isinstance(value, (list, dict)):
                raise BadIngredient('conditional value must be a scalar')
            condition_expression = getattr(field, '__le__')(value)
        elif 'eq' in cond:
            value = cond['eq']
            if isinstance(value, (list, dict)):
                raise BadIngredient('conditional value must be a scalar')
            condition_expression = getattr(field, '__eq__')(value)
        elif 'ne' in cond:
            value = cond['ne']
            if isinstance(value, (list, dict)):
                raise BadIngredient('conditional value must be a scalar')
            condition_expression = getattr(field, '__ne__')(value)
        else:
            raise BadIngredient('Bad condition')

        return condition_expression