@invalidate_table_constraints
    def create_primary_key(self, table_name, columns):
        if not isinstance(columns, (list, tuple)):
            columns = [columns]
        self.execute(self.create_primary_key_string % {
            "table": self.quote_name(table_name),
            "constraint": self.quote_name(table_name + "_pkey"),
            "columns": ", ".join(map(self.quote_name, columns)),
        })
This method creates a generator object and sets the outputs as
dataset/ETHPy150Open cloudera/hue/desktop/core/ext-py/South-1.0.2/south/db/generic.py/DatabaseOperations.create_primary_key--crossover with--dataset/ETHPy150Open VisTrails/VisTrails/vistrails/core/modules/vistrails_module.py/Module.compute_streaming