Prompt error

Hi,

I have got that prompt issue below:

```
Traceback (most recent call last):
File "/Users/okanduzyel/Downloads/segment-anything/testWithPrompt.py", line 23, in
masks, _, _ = predictor.predict("brain tumor")
File "/Users/okanduzyel/Downloads/segment-anything/segment_anything/predictor.py", line 139, in predict
assert (
AssertionError: point_labels must be supplied if point_coords is supplied.
```

My code:

```
import cv2
import matplotlib.pyplot as plt
import numpy as np
import os
import argparse

from segment_anything import SamPredictor, sam_model_registry
sam = sam_model_registry["vit_h"](checkpoint="/Users/okanduzyel/Downloads/segment-anything/sam_vit_h_4b8939.pth")
predictor = SamPredictor(sam)

image_path = '/Users/okanduzyel/Downloads/archive-2/Testing/glioma_tumor/image.jpg' #args.input
img = cv2.imread(image_path)
img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)

predictor.set_image(img)

masks, _, _ = predictor.predict("brain tumor")
```

Any idea?

Start by reading segment_anything/predictor.py around the predict method and the failing call shown in the issue. Compare the accepted inputs with the repository's documented predictor examples; done means the expected prompt usage and required inputs are clearly documented or the issue is shown to be usage-related.

Written by the indexing model from the issue text.