code: def set_default_interface(etree):
      
      global types, ET, modules
  
      t = _get_etree_type(etree)
  
      _types = set(types or [])
      _types.update([t])
  
      types = tuple(_types)
  
      modules[t] = etree
  
      old, ET = ET, etree
  
      return old
docs: Sets the default interface that PyAMF will use to deal with XML entities
      (both objects and blobs).