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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 validate(self):
 """Could this config be used to send a real email?"""

        missing = []
        for k, v in self._map.items():
            attr = getattr(self, k, False)
            if not attr or attr == CONFIG_PLACEHOLDER:
                missing.append(v)
        if missing:
            return "Missing or invalid config values: {}".format(
                ", ".join(sorted(missing))
            )