I was getting same error (TypeError: unhashable type: 'slice') with below code:
included_cols = [2,4,10]
dataset = dataset[:,included_cols] #Columns 2,4 and 10 are included.
Resolved with below code by putting iloc after dataset:
included_cols = [2,4,10]
dataset = dataset.iloc[:,included_cols] #Columns 2,4 and 10 are included.