docs: def get_assembly_names():
      """return list of available assemblies
      
      >>> assy_names = get_assembly_names()
  
      >>> 'GRCh37.p13' in assy_names
      True
  
      """
  
      return [
          n.replace(".json.gz", "")
          for n in pkg_resources.resource_listdir(__name__, _assy_dir)
          if n.endswith(".json.gz")
      ]