I added the lines:
print(f'Mean is of type: {self.mean.type()}')
print(f'std is of type: {self.std.type()}')

And the output was:
Mean is of type: torch.FloatTensor
std is of type: torch.FloatTensor

So it confirms that they were not the correct type. I also added the following two lines:
self.std = self.std.cuda()
self.mean = self.mean.cuda()

Which yielded the output:
Mean is of type: torch.cuda.FloatTensor
std is of type: torch.cuda.FloatTensor

But, when I run the program I get the same error message as before. I went through and checked to see if any other variables were the wrong type and found that ctr_x, ctr_y, widths, and heights were also not the correct type. By changing the device for these variables I was able to run inference.