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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 fact_pk(self):
 """ Try to determine the primary key of the fact table for use in fact table counting. If more than one column exists, return the first column of the pk. """

        keys = [c for c in self.fact_table.columns if c.primary_key]
        return keys[0]