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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 extract_causal_relations(self):
 """Extract causal relations as Statements."""

        # Get the extractions that are labeled as directed and causal
        relations = [e for e in self.doc.extractions if
                     'DirectedRelation' in e['labels'] and
                     'Causal' in e['labels']]
        # For each relation, we try to extract an INDRA Statement and
        # save it if its valid
        for relation in relations:
            stmt = self.get_causal_relation(relation)
            if stmt is not None:
                self.statements.append(stmt)