@classmethod
def _process_attrs(cls, attrs):
    """ Private method for processing attrs.
    Param for this processor got from `get_attrs_processor_param`.
    Param is dict contains two key: `default` and `raname`.
    First add default value to attrs if key does not exist.
    Second rename key to new key.

    For example:
      attrs = {"keep_dims": True}
      param = {"default": {"axis": 1},
               "rename": {"keep_dims": "keepdims"}}

      processed_attrs = {"axis": "1", "keepdims": True}

    :param attrs: Process target attrs.
    :return: Processed attrs.
    """
    param = {'rename': {}, 'default': {}}
    param.update(cls.get_attrs_processor_param())
    for k, v in param['default'].items():
        attrs.setdefault(k, v)
    for k, new_k in param['rename'].items():
        if k in attrs:
            attrs[new_k] = attrs.pop(k)
    return attrs
