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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_feature_variable_integer(self, feature_key, variable_key, user_id, attributes=None):
 """ Returns value for a certain integer variable attached to a feature flag. Args: feature_key: Key of the feature whose variable's value is being accessed. variable_key: Key of the variable whose value is to be accessed. user_id: ID for user. attributes: Dict representing user attributes. Returns: Integer value of the variable. None if: - Feature key is invalid. - Variable key is invalid. - Mismatch with type of variable. """


    variable_type = entities.Variable.Type.INTEGER
    return self._get_feature_variable_for_type(feature_key, variable_key, variable_type, user_id, attributes)