Fix abstract method in options class (#8389)

Co-authored-by: David Burns <david.burns@theautomatedtester.co.uk>

py/selenium/webdriver/common/options.py

@@ -27,6 +27,7 @@ class BaseOptions(object):
     """
 
     def __init__(self):
+        super(BaseOptions, self).__init__()
         self._caps = self.default_capabilities
         self.set_capability("pageLoadStrategy", "normal")
 
@@ -40,12 +41,13 @@ def set_capability(self, name, value):
 
     @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 add_argument(self, argument):
 
     def to_capabilities(self):
         return self._caps
+
+    @property
+    def default_capabilities(self):
+        return {}