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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_by_id(cls, id, parent=None, **ctx_options):
 """Returns an instance of Model class by ID. Args: id: A string or integer key ID. parent: Optional parent key of the model to get. namespace: Optional namespace. app: Optional app ID. **ctx_options: Context options. Returns: A model instance or None if not found. """

    return cls._get_by_id_async(id, parent=parent, **ctx_options).get_result()