def getDevStats(self, dev, devtype = None):
if devtype is not None:<EOL><INDENT>if self._devClassTree is None:<EOL><INDENT>self._initDevClasses()<EOL><DEDENT>if devtype != self._mapDevType.get(dev):<EOL><INDENT>return None<EOL><DEDENT><DEDENT>return self._diskStats.get(dev)<EOL>
Returns I/O stats for block device.

        @param dev:     Device name
        @param devtype: Device type. (Ignored if None.)
        @return:        Dict of stats.