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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 custom_getter(self, activation_dtype=tf.bfloat16):
 """A custom getter that uses the encoding for bfloat16 and float32 vars. When a bfloat16 or float32 variable is requsted, an encoded float16 varaible is created, which is then decoded and cast to a bfloat16 activation. Args: activation_dtype: a dtype to which to convert the decoded value. Returns: a function. """

    def getter_fn(getter, *args, **kwargs):
      requested_dtype = kwargs["dtype"]
      if requested_dtype in (tf.bfloat16, tf.float32):
        kwargs["dtype"] = tf.bfloat16
        kwargs["initializer"] = _EncodingInitializer(
            kwargs["initializer"], self)
        ret = self._decode_with_identity_gradient(getter(*args, **kwargs))
        return tf.cast(ret, activation_dtype)
      return getter(*args, **kwargs)
    return getter_fn