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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 _get_value(self, entity):
 """Internal helper to get the value for this Property from an entity. For a repeated Property this initializes the value to an empty list if it is not set. """

    if entity._projection:
      if self._name not in entity._projection:
        raise UnprojectedPropertyError(
            'Property %s is not in the projection' % (self._name,))
    return self._get_user_value(entity)