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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 set_prior_probs(self, statements):
 """Sets the prior belief probabilities for a list of INDRA Statements. The Statements are assumed to be de-duplicated. In other words, each Statement in the list passed to this function is assumed to have a list of Evidence objects that support it. The prior probability of each Statement is calculated based on the number of Evidences it has and their sources. Parameters statements : list[indra.statements.Statement] A list of INDRA Statements whose belief scores are to be calculated. Each Statement object's belief attribute is updated by this function. """

        self.scorer.check_prior_probs(statements)
        for st in statements:
            st.belief = self.scorer.score_statement(st)