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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 capture_message(self, message, level=None):
 # type: (str, Optional[Any]) -> Optional[str] """Captures a message. The message is just a string. If no level is provided the default level is `info`. """

        if self.client is None:
            return None
        if level is None:
            level = "info"
        return self.capture_event({"message": message, "level": level})