Allow no begin and end block for single row chaining

[xiaodaigh]

@chain df some_function

Allow this syntax where there is only one line

[jkrumbiegel]

I could in theory add that, although I find that usually these sorts of chains are pretty hard to read. Or is it too opinionated not to allow that syntax?

Maybe you could give a more "real world" example that you need. @chain df some_function is normally going to be written as some_function(df) of course

[xiaodaigh]

No worries. Not important