docs: @Requires({
      "processingEnv != null",
      "element != null"
    })
    @Ensures("result != null")
    public static Set<String> getImportNames(ProcessingEnvironment processingEnv,
        Element element) {
      Trees treeUtils = Trees.instance(processingEnv);
      if (treeUtils == null) {
        return Collections.emptySet();
      }
  
      TreePath path = treeUtils.getPath(element);
      if (path == null) {
        return Collections.emptySet();
      }
  
      CompilationUnitTree unitTree = path.getCompilationUnit();
  
      HashSet<String> importNames = new HashSet<String>();
      for (ImportTree importTree : unitTree.getImports()) {
        StringBuilder buffer = new StringBuilder();
        if (importTree.isStatic()) {
          buffer.append("static ");
        }
        /* TODO(lenh): Roll our own toString()? */
        buffer.append(importTree.getQualifiedIdentifier().toString());
        importNames.add(buffer.toString());
      }
  
      return importNames;
    }