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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 hdel(self, *args):
 """ This command on the model allow deleting many instancehash fields with only one redis call. You must pass hash names to retrieve as arguments """

        if args and not any(arg in self._instancehash_fields for arg in args):
            raise ValueError("Only InstanceHashField can be used here.")

        # Set indexes for indexable fields.
        for field_name in args:
            field = self.get_field(field_name)
            if field.indexable:
                field.deindex()

        # Return the number of fields really deleted
        return self._call_command('hdel', *args)