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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_validated_field(fld, selectable):
 """ Converts a validated field to sqlalchemy. Field references are looked up in selectable """

    aggr_fn = IngredientValidator.aggregation_lookup[fld['aggregation']]

    field = find_column(selectable, fld['value'])

    for operator in fld.get('operators', []):
        op = operator['operator']
        other_field = parse_validated_field(operator['field'], selectable)
        field = IngredientValidator.operator_lookup[op](field)(other_field)

    condition = fld.get('condition', None)
    if condition:
        condition = parse_condition(condition, selectable)
        field = case([(condition, field)])

    field = aggr_fn(field)
    return field