Here's an idea to make it generic.

See this snippet in naarad_imports:
```
important_sub_metrics_import = {
    'GC': ('GCPause', 'used'),
    'LINKEDINANDROIDRUM': ('launch_time', 'nus_update_time'),
    'SAR-cpuusage': ('%sys', '%usr'),
    'SAR-device': ('%util', 'await'),
    'JMETER': ('Overall_Summary.ResponseTime', 'Overall_Summary.DataThroughput', 'Overall_Summary.qps')
}

device_type_metrics = ('SAR-cpuusage', 'SAR-cpuhz', 'SAR-device', 'SAR-dev', 'SAR-edev')
```

So, `important_sub_metric` can contain just the submetric name (`launch_time`, `%util`) or also the "device name" + submetric name (`Overall_Summary.ResponseTime`).

We should cover both cases. If a metric is in `device_type_metrics` set above (Jmeter should be added to that set), then check if both `items[-1]` or `'.'join(items[-2:])` are in `self.important_sub_metrics`.

How's that?