A type that determines how metrics should be interpreted.
Values:
METRICS_TYPE_UNSPECIFIED (0):
The metrics type is unspecified. By default,
metrics without a particular specification are
for leaf entity types (i.e., top-level entity
types without child types, or child types which
are not parent types themselves).
AGGREGATE (1):
Indicates whether metrics for this particular
label type represent an aggregate of metrics for
other types instead of being based on actual
TP/FP/FN values for the label type. Metrics for
parent (i.e., non-leaf) entity types are an
aggregate of metrics for their children.