BruteForce layer cannot be built with tf.string identifiers

[comckay]

Currently, on version 0.7.3 BruteForce within layers.factorized_top_k cannot be built with identifiers of type tf.string.

Simple example that works with identifiers as tf.int64

tfrs.layers.factorized_top_k.BruteForce(k=10).index(candidates=tf.random.normal((200,100)), identifiers=tf.constant([_ for _ in range(200)], dtype=tf.int64))

Simple example that does not work throwing an error when creating variables in the background

tfrs.layers.factorized_top_k.BruteForce(k=10).index(candidates=tf.random.normal((200,100)), identifiers=tf.constant([str(_) for _ in range(200)], dtype=tf.string))

Full trace here

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[25], line 1
----> 1 tfrs.layers.factorized_top_k.BruteForce(k=10).index(candidates=tf.random.normal((200,100)), identifiers=tf.constant([str(_) for _ in range(200)], dtype=tf.string))

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/tensorflow_recommenders/layers/factorized_top_k.py:550](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/tensorflow_recommenders/layers/factorized_top_k.py#line=549), in BruteForce.index(self, candidates, identifiers)
    547 # We need any value that has the correct dtype.
    548 identifiers_initial_value = tf.zeros((), dtype=identifiers.dtype)
--> 550 self._identifiers = self.add_weight(
    551     name="identifiers",
    552     dtype=identifiers.dtype,
    553     shape=identifiers.shape,
    554     initializer=tf.keras.initializers.Constant(
    555         value=identifiers_initial_value),
    556     trainable=False)
    557 self._candidates = self.add_weight(
    558     name="candidates",
    559     dtype=candidates.dtype,
    560     shape=candidates.shape,
    561     initializer=tf.keras.initializers.Zeros(),
    562     trainable=False)
    564 self._identifiers.assign(identifiers)

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/layers/layer.py:546](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/layers/layer.py#line=545), in Layer.add_weight(self, shape, initializer, dtype, trainable, autocast, regularizer, constraint, aggregation, name)
    544 initializer = initializers.get(initializer)
    545 with backend.name_scope(self.name, caller=self):
--> 546     variable = backend.Variable(
    547         initializer=initializer,
    548         shape=shape,
    549         dtype=dtype,
    550         trainable=trainable,
    551         autocast=autocast,
    552         aggregation=aggregation,
    553         name=name,
    554     )
    555 # Will be added to layer.losses
    556 variable.regularizer = regularizers.get(regularizer)

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/common/variables.py:186](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/common/variables.py#line=185), in Variable.__init__(self, initializer, shape, dtype, trainable, autocast, aggregation, name)
    184 if callable(initializer):
    185     self._shape = self._validate_shape(shape)
--> 186     self._initialize_with_initializer(initializer)
    187 else:
    188     self._initialize(initializer)

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/tensorflow/core.py:48](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/tensorflow/core.py#line=47), in Variable._initialize_with_initializer(self, initializer)
     47 def _initialize_with_initializer(self, initializer):
---> 48     self._initialize(lambda: initializer(self._shape, dtype=self._dtype))

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/tensorflow/core.py:39](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/tensorflow/core.py#line=38), in Variable._initialize(self, value)
     38 def _initialize(self, value):
---> 39     self._value = tf.Variable(
     40         value,
     41         dtype=self._dtype,
     42         trainable=self.trainable,
     43         name=self.name,
     44         aggregation=self._map_aggregation(self.aggregation),
     45     )

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/tensorflow/python/util/traceback_utils.py:153](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/tensorflow/python/util/traceback_utils.py#line=152), in filter_traceback.<locals>.error_handler(*args, **kwargs)
    151 except Exception as e:
    152   filtered_tb = _process_traceback_frames(e.__traceback__)
--> 153   raise e.with_traceback(filtered_tb) from None
    154 finally:
    155   del filtered_tb

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/tensorflow/core.py:48](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/tensorflow/core.py#line=47), in Variable._initialize_with_initializer.<locals>.<lambda>()
     47 def _initialize_with_initializer(self, initializer):
---> 48     self._initialize(lambda: initializer(self._shape, dtype=self._dtype))

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/initializers/constant_initializers.py:36](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/initializers/constant_initializers.py#line=35), in Constant.__call__(self, shape, dtype)
     34 def __call__(self, shape, dtype=None):
     35     dtype = standardize_dtype(dtype)
---> 36     return ops.cast(self.value, dtype=dtype) * ops.ones(
     37         shape=shape, dtype=dtype
     38     )

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/ops/numpy.py:6589](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/ops/numpy.py#line=6588), in ones(shape, dtype)
   6578 @keras_export(["keras.ops.ones", "keras.ops.numpy.ones"])
   6579 def ones(shape, dtype=None):
   6580     """Return a new tensor of given shape and type, filled with ones.
   6581 
   6582     Args:
   (...)
   6587         Tensor of ones with the given shape and dtype.
   6588     """
-> 6589     return backend.numpy.ones(shape, dtype=dtype)

File [~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/tensorflow/numpy.py:704](http://localhost:8888/lab/tree/~/dev/scratchpad/factorized_top_k_debugging/.venv/lib/python3.10/site-packages/keras/src/backend/tensorflow/numpy.py#line=703), in ones(shape, dtype)
    702 def ones(shape, dtype=None):
    703     dtype = dtype or config.floatx()
--> 704     return tf.ones(shape, dtype=dtype)

TypeError: Cannot convert 1 to EagerTensor of dtype string