How to provide artifacts for transforms

i’m trying to provide the Android Gradle plugin 3.3.2 with artifacts, injecting them into its transform graph, but i can’t get the Android plugin to pick them up.

for example, say i have directory X and i want to offer it to the plugin as an EXPLODED_AAR artifact. that is:

import static org.gradle.api.internal.artifacts.ArtifactAttributes.ARTIFACT_FORMAT;
import static com.android.build.gradle.internal.publishing.AndroidArtifacts.ArtifactType.EXPLODED_AAR;

// i want my directory X to be tagged with this attribute:
attribute(ARTIFACT_FORMAT, EXPLODED_AAR.getType())

for reference, a sample of code in the Android plugin that should consume my artifact follows:

project.dependencies.registerTransform(
                reg -> {
                    reg.getFrom().attribute(ARTIFACT_FORMAT, EXPLODED_AAR.getType());
                    reg.getTo()
                            .attribute(
                                    ARTIFACT_FORMAT,
                                    ArtifactType.SYMBOL_LIST_WITH_PACKAGE_NAME.getType());
                    reg.artifactTransform(LibrarySymbolTableTransform.class);
                });

how do i go about offering my directory as such an artifact?
thanks!