'Returns metric value of a given metric for given fields values.
Args:
varname: Metric name:
fields: List of values for this metric\'s fields. For example, if metric
was registered with fields like
[("flow_type", int), ("user_type", int)], then for that metric
fields argument may look like: fields=[10, 12]. Should be None
if the metric was registered without any fields.
Returns:
int for a counter metric.
int, long, float, str or bool (depending on the type used to register
the metric) for a gauge metric.
Distribtion-compatible object for event metric. Distribution-compatible
means "with an API matching the API of the Distribution object".'

def GetMetricValue(self, varname, fields=None):

    return self._metrics[varname].Get(fields)
