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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 create(self):
 """Create the table underlying the queue. Create the 'metadata' and 'tfexample' column families and their properties. """

        if self.bt_table.exists():
            utils.dbg('Table already exists')
            return

        max_versions_rule = bigtable_column_family.MaxVersionsGCRule(1)
        self.bt_table.create(column_families={
            METADATA: max_versions_rule,
            TFEXAMPLE: max_versions_rule})