Regular expressions in regular strings generate deprecation warnings
with Python 3 ("invalid escape sequence \x"). To fix these warnings,
the regex must be contained within a raw string. For nodes that have
parameters whose description and/or value contain regex, the strings
are transformed into raw strings. In the case of descriptions, which are
generally written across several lines, regular strings are concatenated
with regular strings to preserve line returns (with "\n", which becomes
uneffective in raw strings).
