No worries! Actually, I was looking for an example like you suggested and I couldn't find one quite the same. However, if you have a look at this metric:
you can see that it can actually return either a dictionary or a single number (fancy! most just choose one or the other).
The varMetrics.py file has another example of a metric that returns a dictionary:
and this one
returns an array.
Both of these simply store the metric values at each point in a numpy object array.
The "vector metrics" we have, at
are more specialized .. the dimension at each slicepoint is assumed to be time, the metricValues are stored as a two-d array (instead of one-dimensional object array), and there are some special plotters that can interpret and deal with this information directly.