Fix abstract method in options class (#8389)

Co-authored-by: David Burns <david.burns@theautomatedtester.co.uk>
Cr-Mirrored-From: https://chromium.googlesource.com/external/github.com/SeleniumHQ/selenium
Cr-Mirrored-Commit: 90e3cc5d56ffd7eb272348ebaec359452d2d13e8
diff --git a/selenium/webdriver/common/options.py b/selenium/webdriver/common/options.py
index fa58ae2..bff2517 100644
--- a/selenium/webdriver/common/options.py
+++ b/selenium/webdriver/common/options.py
@@ -27,6 +27,7 @@
     """
 
     def __init__(self):
+        super(BaseOptions, self).__init__()
         self._caps = self.default_capabilities
         self.set_capability("pageLoadStrategy", "normal")
 
@@ -40,12 +41,13 @@
 
     @abstractmethod
     def to_capabilities(self):
-        return
+        """Convert options into capabilities dictionary."""
 
     @property
     @abstractmethod
     def default_capabilities(self):
-        return {}
+        """Return minimal capabilities necessary as a dictionary."""
+
 
 
 class ArgOptions(BaseOptions):
@@ -75,3 +77,7 @@
 
     def to_capabilities(self):
         return self._caps
+
+    @property
+    def default_capabilities(self):
+        return {}