ImmutableList<String> exceptionStacks() {
    return ImmutableList.copyOf(exceptionStacks);
  }
<ol>
  <li>For each class annotated with {@link AutoService}
      <ul>
        <li>Verify the {@link AutoService} interface value is correct
        <li>Categorize the class by its service interface
      </ul>
  <li>For each {@link AutoService} interface
      <ul>
        <li>Create a file named {@code META-INF/services/<interface>}
        <li>For each {@link AutoService} annotated class for this interface
            <ul>
              <li>Create an entry in the file
            </ul>
      </ul>
</ol>
service/processor/src/main/java/com/google/auto/service/processor/AutoServiceProcessor.java