question: TPU on Colab: unexpected keyword argument 'num_tpu_cores'
context: On a Colab TPU, I get the error:
  File "/usr/local/lib/python3.7/dist-packages/pytorch_lightning/trainer/connectors/env_vars_connector.py", line 42, in overwrite_by_env_vars
      return fn(self, **kwargs)
  TypeError: __init__() got an unexpected keyword argument 'num_tpu_cores'
  
  I'm running a script that is in my Google Drive. I copy the data up onto Colab. When I do the exact same process for the GPU, it works (with Colab set to GPU, and the appropriate trainer parameter adjustment).
  The trainer instantiation is simply
      trainer = pl.Trainer(logger=logger,
                           num_tpu_cores=8,
                           fast_dev_run=False,
                           max_epochs=20)
answer: @naraugialusru num_tpu_cores should be tpu_cores. num_tpu_cores was removed in #2760. See also: the docs