code: def _repr(self, params):
      kvs = [f"{k}={v}" for k, v in params.items() if v is not None]
      return "{} [{}]".format(self._repr_name(), ",".join(kvs))
  
file_path: mars/mars/dataframe/window/core.py
imports: from ...serialization.serializables import Serializable, KeyField
label_desc: Use image node_id 4 for calling the Window obj's underlying member method code with example usage: obj._repr(params) and returns: str