Correct some regular expression syntax. (#2577)

* Correct some badly-formed regular expressions.

Author: georgevdd

Diff for: packages/python/plotly/codegen/datatypes.py

@@ -117,7 +117,7 @@ class {datatype_class}(_{node.name_base_datatype}):\n"""
     
     import re
     _subplotid_prop_re = re.compile(
-        '^(' + '|'.join(_subplotid_prop_names) + ')(\d+)$')
+        '^(' + '|'.join(_subplotid_prop_names) + r')(\d+)$')
 """
         )
 

Diff for: packages/python/plotly/plotly/basedatatypes.py

@@ -23,7 +23,7 @@ class BaseFigure(object):
     Base class for all figure types (both widget and non-widget)
     """
 
-    _bracket_re = re.compile("^(.*)\[(\d+)\]$")
+    _bracket_re = re.compile(r"^(.*)\[(\d+)\]$")
 
     _valid_underscore_properties = {
         "error_x": "error-x",

Diff for: packages/python/plotly/plotly/graph_objs/_layout.py

@@ -17,7 +17,7 @@ class Layout(_BaseLayoutType):
 
     import re
 
-    _subplotid_prop_re = re.compile("^(" + "|".join(_subplotid_prop_names) + ")(\d+)$")
+    _subplotid_prop_re = re.compile("^(" + "|".join(_subplotid_prop_names) + r")(\d+)$")
 
     @property
     def _subplotid_validators(self):