class_docstr: Generic class for a recommender model. All recommendation models should inherit from this class.
  
  Parameters
  ----------------
  name: str, required
      Name of the recommender model.
  
  trainable: boolean, optional, default: True
      When False, the model is not trainable.
  
  verbose: boolean, optional, default: False
      When True, running logs are displayed.
  
  Attributes
  ----------
  num_users: int
      Number of users in training data.
  
  num_items: int
      Number of items in training data.
  
  total_users: int
      Number of users in training, validation, and test data.
      In other words, this includes unknown/unseen users.
  
  total_items: int
      Number of items in training, validation, and test data.
      In other words, this includes unknown/unseen items.
  
  uid_map: int
      Global mapping of user ID-index.
  
  iid_map: int
      Global mapping of item ID-index.
  
  max_rating: float
      Maximum value among the rating observations.
  
  min_rating: float
      Minimum value among the rating observations.
  
  global_mean: float
      Average value over the rating observations.
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docstr: Return whether the model knows item by its index. Reverse of knows_item() function,
  for better readability in some cases.
  
  Parameters
  ----------
  item_idx: int, required
      The index of the item (not the original item ID).
  
  Returns
  -------
  res : bool
      True if model knows the item from traning data, False otherwise.
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code: def is_unknown_item(self, item_idx):
      """Return whether the model knows item by its index. Reverse of knows_item() function,
      for better readability in some cases.
  
      Parameters
      ----------
      item_idx: int, required
          The index of the item (not the original item ID).
  
      Returns
      -------
      res : bool
          True if model knows the item from traning data, False otherwise.
      """
      return not self.knows_item(item_idx)
  
imports: import copy
  import inspect
  import os
  import pickle
  import warnings
  from datetime import datetime
  from glob import glob
  import numpy
  from ..exception import ScoreException
  from ..utils.common import clip
label_desc: Use image node_id 16 for calling the Recommender obj's underlying member method code with example usage: obj.is_unknown_item(item_idx) and returns: unknown