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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 check_config(self, config, fields_spec):
 """ Check that `config` has each field in `fields_spec` if a default has not been provided. """

        for field, type_info in fields_spec.items():
            has_default = not isinstance(type_info, type)
            if field not in config and not has_default:
                raise RuntimeError(
                    "Configuration not complete. %s missing" % field)