Export Blender data into directory through a directory browser

Question

I’d like to use a directory browser. I’m using the ExportHelper class, but it pops a file browser. Is there anything special to turn it into a directory browser?

Here’s some code:

class ExampleExporter(bpy.types.Operator, ExportHelper):
  """My Mesh Exporter Script"""
  bl_idname      = "object.example_mesh_exporter"
  bl_label       = "Example Mesh Exporter"
  bl_description = "Export all meshes from the scene into a directory"
  bl_options     = {'REGISTER'}

  filename_ext   = ".huhu" # I don’t even need that

  sparse = BoolProperty (
      name        = "Sparse output"
    , description = "Should the output file be sparse?"
    , default     = False
    , )

  def execute(self, context):
    # do something with self.filepath

I don’t need self.filepath, I’d need something like self.directory..