Finding your custom plugin
nodes within a scene.
When you create any custom node which you add into Maya via a
plugin, you need to specify a unique MTypeId so that Maya can
distinguish your plugin node type from other node types.
When we wish to find a specific node type that we have added
into maya, we need to use the typeId() member of MFnDependencyNode
to check the node type against the TypeId we assigned to the node.
In this example, MyNodeType is the custom plugin node that would
have been derived from MPxNode.