Fix deprecation warnings due to invalid escape sequences.

Author: tirkarthi

lib/pyld/jsonld.py

@@ -5197,7 +5197,7 @@ def _create_term_definition(self, active_ctx, local_ctx, term, defined, options,
                 mapping['_prefix'] = (
                     _simple_term and
                     not mapping['_term_has_colon'] and
-                    bool(re.match('.*[:/\?#\[\]@]$', id_)))
+                    bool(re.match(r'.*[:/\?#\[\]@]$', id_)))
         if '@id' not in mapping:
             # see if the term has a prefix
             if mapping['_term_has_colon']: