`type_as` bug in the doc of LightningModule
🐛 Bug
When I run this line of code in the doc, it complains that type_as shouldn't be given a str.
To Reproduce
Code sample

The last line of the following code
x = torch.zeros(2, device='cpu')
new_x = torch.zeros(3, device='cuda:0')
new_x = new_x.type_as(x.type())
gives this error:
TypeError: type_as(): argument 'other' (position 1) must be Tensor, not str

Expected behavior
Cast new_x to the same type as x.
A potential fix:
new_x = new_x.type_as(x)
Environment
* CUDA:
        - GPU:
                - GeForce RTX 2080
                - GeForce RTX 2080
        - available:         True
        - version:           10.2
* Packages:
        - numpy:             1.18.5
        - pyTorch_debug:     False
        - pyTorch_version:   1.5.1
        - pytorch-lightning: 0.9.0rc5
        - tensorboard:       2.2.2
        - tqdm:              4.47.0
* System:
        - OS:                Linux
        - architecture:
                - 64bit
                - ELF
        - processor:         x86_64
        - python:            3.8.3
        - version:           #113-Ubuntu SMP Thu Jul 9 23:41:39 UTC 2020