remove public Collection() function on ExtensionRegistry

Author: benbellick

expr/expression.go

@@ -1612,7 +1612,7 @@ func ExtendedFromProto(ex *proto.ExtendedExpression, c *extensions.Collection) (
 }
 
 func (ex *Extended) ToProto() *proto.ExtendedExpression {
-	urns, uris, decls := ex.Extensions.ToProto(ex.reg.Collection())
+	urns, uris, decls := ex.reg.ExtensionsToProto()
 	refs := make([]*proto.ExpressionReference, len(ex.ReferredExpr))
 	for i, ref := range ex.ReferredExpr {
 		refs[i] = ref.ToProto()

expr/utils.go

@@ -6,6 +6,7 @@ import (
 	"github.com/substrait-io/substrait-go/v6/extensions"
 	"github.com/substrait-io/substrait-go/v6/types"
 	proto "github.com/substrait-io/substrait-protobuf/go/substraitpb"
+	extensionspb "github.com/substrait-io/substrait-protobuf/go/substraitpb/extensions"
 )
 
 // ExtensionRegistry provides functionality to resolve extension references and handle subquery expressions.
@@ -76,7 +77,7 @@ func (e *ExtensionRegistry) LookupWindowFunction(anchor uint32) (*extensions.Win
 	return e.Set.LookupWindowFunction(anchor, e.c)
 }
 
-// Collection returns the underlying extensions collection.
-func (e *ExtensionRegistry) Collection() *extensions.Collection {
-	return e.c
+// ExtensionsToProto returns the URNs, URIs, and declarations from the extension set using the registry's collection.
+func (e *ExtensionRegistry) ExtensionsToProto() ([]*extensionspb.SimpleExtensionURN, []*extensionspb.SimpleExtensionURI, []*extensionspb.SimpleExtensionDeclaration) {
+	return e.Set.ToProto(e.c)
 }

plan/plan.go

@@ -233,7 +233,7 @@ func FromProto(plan *proto.Plan, c *extensions.Collection) (*Plan, error) {
 }
 
 func (p *Plan) ToProto() (*proto.Plan, error) {
-	urns, uris, decls := p.extensions.ToProto(p.reg.Collection())
+	urns, uris, decls := p.reg.ExtensionsToProto()
 	relations := make([]*proto.PlanRel, len(p.relations))
 	for i, r := range p.relations {
 		relations[i] = r.ToProto()