I have cloned the repository for U-net with tensorflow.

```
labels = np.zeros((ny, nx, self.n_class), dtype=np.float32)
labels[..., 1] = label
labels[..., 0] = ~label

```

I get an error in the 3rd line saying:

**TypeError**: ufunc '**invert**' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''**safe**''

How do I debug this?