This seems to need tightening up

Causes unwanted complication in variable-length-strings workaround example : seen here

• in this case, needed to assign var.dtype after replacing var.data
• .. without which, the variable doesn't save as a char-array (which is the whole point)

Also relates to #88

Also

A good time to enforce that variable.data is always a numpy array.
Currently if you break this, nasty things happen.

Note:

when fixed, remove these lines in code example