code: def _get_default(self, obj):
          ''' Internal implementation of instance attribute access for default
          values.
  
          Handles bookeeping around |PropertyContainer| value, etc.
  
          '''
          if self.name in obj._property_values:
              # this shouldn't happen because we should have checked before _get_default()
              raise RuntimeError("Bokeh internal error, does not handle the case of self.name already in _property_values")
  
          is_themed = obj.themed_values() is not None and self.name in obj.themed_values()
  
          default = self.instance_default(obj)
  
          if is_themed:
              unstable_dict = obj._unstable_themed_values
          else:
              unstable_dict = obj._unstable_default_values
  
          if self.name in unstable_dict:
              return unstable_dict[self.name]
  
          if self.property._may_have_unstable_default():
              if isinstance(default, PropertyValueContainer):
                  default._register_owner(obj, self)
              unstable_dict[self.name] = default
  
          return defaulf _get_default(self, obj):
          ''' Internal implementation of instance attribute access for default
          values.
  
          Handles bookeeping around |PropertyContainer| value, etc.
  
          '''
          if self.name in obj._property_values:
              # this shouldn't happen because we should have checked before _get_default()
              raise RuntimeError("Bokeh internal error, does not handle the case of self.name already in _property_values")
  
          is_themed = obj.themed_values() is not None and self.name in obj.themed_values()
  
          default = self.instance_default(obj)
  
          if is_themed:
              unstable_dict = obj._unstable_themed_values
          else:
              unstable_dict = obj._unstable_default_values
  
          if self.name in unstable_dict:
              return unstable_dict[self.name]
  
          if self.property._may_have_unstable_default():
              if isinstance(default, PropertyValueContainer):
                  default._register_owner(obj, self)
              unstable_dict[self.name] = default
  
          return default
docs: Internal implementation of instance attribute access for default
          values.
  
          Handles bookeeping around |PropertyContainer| value, etc.