x =(x, label) ¶Requires that input is a cellstr.
Raises an error if the input x is not a cellstr (a cell array
of char arrays).
TODO: Decide whether to require the contained char arrays be rowvec/empty.
label is an optional input that determines how the input will be described in
error messages. If not supplied, inputname (1) is used, and if that is
empty, it falls back to "input".