tensorflow/models · error · ValueError

Block fn `{}` is not supported.

Error message

Block fn `{}` is not supported.

What it means

Error "Block fn `{}` is not supported." thrown in tensorflow/models.

Source

Thrown at official/vision/modeling/backbones/resnet_deeplab.py:250

      x = self._norm(
          axis=bn_axis,
          momentum=norm_momentum,
          epsilon=norm_epsilon,
          synchronized=use_sync_bn)(
              x)
      x = tf_utils.get_activation(activation, use_keras_layer=True)(x)
    else:
      x = layers.MaxPool2D(pool_size=3, strides=2, padding='same')(x)

    normal_resnet_stage = int(math.log2(self._output_stride)) - 2

    endpoints = {}
    for i in range(normal_resnet_stage + 1):
      spec = RESNET_SPECS[model_id][i]
      if spec[0] == 'bottleneck':
        block_fn = nn_blocks.BottleneckBlock
      else:
        raise ValueError('Block fn `{}` is not supported.'.format(spec[0]))
      x = self._block_group(
          inputs=x,
          filters=spec[1],
          strides=(1 if i == 0 else 2),
          dilation_rate=1,
          block_fn=block_fn,
          block_repeats=spec[2],
          stochastic_depth_drop_rate=nn_layers.get_stochastic_depth_rate(
              self._init_stochastic_depth_rate, i + 2, 4 + last_stage_repeats),
          name='block_group_l{}'.format(i + 2))
      endpoints[str(i + 2)] = x

    dilation_rate = 2
    for i in range(normal_resnet_stage + 1, 3 + last_stage_repeats):
      spec = RESNET_SPECS[model_id][i] if i < 3 else RESNET_SPECS[model_id][-1]
      if spec[0] == 'bottleneck':
        block_fn = nn_blocks.BottleneckBlock
      else:

View on GitHub (pinned to e006f5f0d5)

Solutions

1. Use a supported block_fn: 'bottleneck' or 'basic'.
2. Check the block_fn value in the backbone config for typos.

When it happens

Trigger: Thrown at official/vision/modeling/backbones/resnet_deeplab.py:250 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of tensorflow/models@e006f5f0d5 (2026-08-24). Data as JSON: /api/errors/4601f3c207f722f3. Report an issue: GitHub.