func (g *expansionGenerator) Filter(c *generator.Context, t *types.Type) bool {
	return t == g.types[0]
}
We only want to call GenerateType() once per group.
package generators
import (
	"io"
	"os"
	"path/filepath"
	"strings"
	"k8s.io/gengo/generator"
	"k8s.io/gengo/types"
	"k8s.io/code-generator/cmd/client-gen/generators/util"
)
type expansionGenerator struct {
	generator.DefaultGen
	packagePath string
	types       []*types.Type
}