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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 _properties_model_to_dict(properties):
 """ Convert properties model to dict. Args: properties: Properties model. Returns: dict: Converted model. """

    result = {}
    for attr in properties.__dict__:
        value = getattr(properties, attr)

        if hasattr(value, '__module__') and 'models' in value.__module__:
            value = _properties_model_to_dict(value)

        if not (value is None or (isinstance(value, dict) and not value)):
            result[attr] = value

    return result