def load(self, content):
        """Loads Packet Definitions from the given YAML content into this
        Telemetry Dictionary.  Content may be either a filename
        containing YAML content or a YAML string.

        Load has no effect if this Command Dictionary was already
        instantiated with a filename or YAML content.
        """
        if self.filename is None:
            if os.path.isfile(content):
                self.filename = content
                stream        = open(self.filename, 'rb')
            else:
                stream        = content

            pkts = yaml.load(stream)
            pkts = handle_includes(pkts)
            for pkt in pkts:
                self.add(pkt)

            if type(stream) is file:
                stream.close()