Issue in `create_rank` function if we pass hrvar as string parameter then throwing keyword error

[sachinstl]

In create_rank function, we can either give string or list of strings for hrvar parameter as per function definition, but when I give string for hrvar parameter, it is throwing keyword error.

create_rank(data = pq_data_small, hrvar = "FunctionType", metric = "Emails_sent", return_type = "plot")

The same works if we pass it as a list:

Either we should only accept list of strings for hrvar parameter or we should handle the case when hrvar is string.