Control how families are matched amongst plug-ins and instances.

The way instances are associated with plug-ins are via their `families`

.

Instances and plug-ins may support one or more families, and instances matching one or more of these families are said to be associated with it.

An instance may be associated via a plug-in in 1 of 3 ways.

Intersection

Subset

Exact

By default, an instance of any family within the supported families of a plug-in is a match. This is called **Intersection** and stems from basic set theory.

assert set(["a", "b"]).intersection(["b", "c"])

This is useful in the most general case, of one plug-in supporting many different - possibly unrelated - families. Such as one plug-in supporting both models and rigs, say for an established naming convention across both families.

**Subset** on the other hand means the families of an Instance must be a *subset* of the supported families of any plug-in.

Again the concept is borrowed from set theory.

assert set(["a", "b"]).issubset(["a", "b", "c"])

This can be useful when instances are specialised, such as being a `lowpoly`

family of a `model`

, or `animation`

family of a `rig`

.

Finally, there is **Exact** which captures edge-cases or otherwise highly context sensitive instances, such as an `animation`

`rig`

in `shot05`

.

The algorithm is as follows.

assert set(["a", "b"]) == set(["b", "a"])

Decide whether your plug-in targets many unrelated families, or specialises in a few, then associate an algorithm with this plug-in.

**Example**

In this example, `SpecificPlugin`

is associated to instances whose family(ies) are a **subset** of the supported families model and low. If the instance does not have at least both of these, it is not a match.

This is different from `GenericPlugin`

, where only one of the families of an instance need to match any of the supported families of a plug-in. This is called **intersection**.

from pyblish import apiâ€‹class GenericPlugin(api.InstancePlugin):# Support both models and rigsfamilies = ["model", "rig"]â€‹def process(self, instance):# Applies to both models and rigsassert "parent_GRP" in instanceâ€‹class SpecificPlugin(api.InstancePlugin):# Support models, but only low-poly modelsfamilies = ["model", "low"]match = api.Subsetâ€‹def process(self, instance):# Safe to assume it has a `polyCount` due# to only capturing models.assert instance.data["polyCount"] < 500

The last possible value is `Exact`

which means an instance only matches when families of both instance and plug-ins match exactly.

class EdgeCasePlugin(api.InstancePlugin):families = ["model", "low", "level21"]match = api.Exactâ€‹def process(self, instance):assert "specialMember" in instance