Append a 'wait' command to the script. The set value of this
object should be the maximum waiting time for the packet
containing the content configured in the last expect command.
Wait time is in units of milliseconds, and the maximum
supported is 65535 ms. The 'wait ' characters will be
automatically appended. Also a 'null terminator'(\0) will be
automatically appended. The null terminator and the 'wait '
characters will be counted as characters in the script. When
read, the return value has no significant meaning, but a 1 is
always returned.