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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 role(self, role_name):
 """ Set role of current column :param role_name: name of the role to be selected. :return: """

        field_name = self.name
        field_roles = {field_name: MLField.translate_role_name(role_name)}
        if field_roles:
            return _change_singleton_roles(self, field_roles, True)
        else:
            return self