OSError: Specfile not found at: spec.txt when use Transfer Learning Toolkit-3.0 to Train

After I have installed the nvidia-tlt, now I want to train the unet model of TLT3.0.

run command: tlt unet train -r /workspace -e spec.txt -k key --gpus 1

Got error: OSError: Specfile not found at: spec.txt

But in the workspace directory, I have a spec.txt file.

Can please suggest how to fix this problem?
Thanks
Jimmy

use_amp: False
warmup_steps: 1000
checkpoint: “./resnet101/resnet_101.hdf5”

data_config{
image_size: “(832, 1344)”
augment_input_data: True
eval_samples: 5000
training_file_pattern: “DATA/train*.tfrecord”
validation_file_pattern: “DATA/val*.tfrecord”
val_json_file: “./DATA/raw-data/annotations/instances_val2017.json”
num_classes: 91
skip_crowd_during_training: True
}
model_config {
num_layers: 18
all_projections: true
arch: “resnet”
freeze_blocks: 0
freeze_blocks: 1
use_batch_norm: true
training_precision {
backend_floatx: FLOAT32
}
model_input_height: 320
model_input_width: 320
model_input_channels: 3
}
training_config {
batch_size: 2
epochs: 3
log_summary_steps: 10
checkpoint_interval: 1
loss: “cross_dice_sum”
learning_rate:0.0001
regularizer {
type: L2
weight: 3.00000002618e-09
}
optimizer {
adam {
epsilon: 9.99999993923e-09
beta1: 0.899999976158
beta2: 0.999000012875
}
}
}