ContextMenu on LineArrowAnnotation/Text and Custom Annotations

How do I create Context menu for the extended versions of the annotations? Please see my code below: I am getting an error PART is missing at runtime:

    <Style x:Key="LineArrowExdendedAnnotationStyle" TargetType="local:LineArrowExdendedAnnotation">
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="local:LineArrowExdendedAnnotation">
                    <Grid x:Name="PART_LineArrowAnnotationRoot" Width="{TemplateBinding Width}"
                        Margin="{TemplateBinding Margin}">
                        <Grid.ContextMenu>
                            <ContextMenu>
                                <MenuItem Command="Cut">
                                </MenuItem>
                                <MenuItem Command="Copy">
                                </MenuItem>
                                <MenuItem Command="Paste">
                                </MenuItem>
                            </ContextMenu>
                        </Grid.ContextMenu>
                    </Grid>
                </ControlTemplate>

            </Setter.Value>
        </Setter>
    </Style>