add_dimension.py

        props2 = layout.operator("curve.dimension", text = 'Add 3D angle dimension')
        props2.Dimension_Change = False
        props2.Dimension_Type = 'Angular1'
        props2.Dimension_width_or_location = 'location'
        props2.Dimension_startlocation = startvertex
        props2.Dimension_endlocation = endvertex
        props2.Dimension_endanglelocation = endanglevertex
        props2.Dimension_liberty = '3D'
        props2.Dimension_rotation = 0
        props2.Dimension_parent = obj.name

def Dimension_button(self, context):
    oper = self.layout.operator(Dimension.bl_idname, text = "Dimension", icon = "PLUGIN")
    oper.Dimension_Change = False
    oper.Dimension_width_or_location = 'width'
    oper.Dimension_liberty = '2D'

################################################################################
##### REGISTER #####
classes = [
    Dimension,
]

def register():
    from bpy.utils import register_class
    for cls in classes:
        register_class(cls)

    bpy.types.VIEW3D_MT_curve_add.append(Dimension_button)
    bpy.types.VIEW3D_MT_object_context_menu.prepend(Dimension_object_menu)
    bpy.types.VIEW3D_MT_edit_mesh_context_menu.append(Dimension_edit_menu)

def unregister():
    bpy.types.VIEW3D_MT_edit_mesh_context_menu.remove(Dimension_edit_menu)
    bpy.types.VIEW3D_MT_object_context_menu.remove(Dimension_object_menu)
    bpy.types.VIEW3D_MT_curve_add.remove(Dimension_button)

    from bpy.utils import unregister_class
    for cls in reversed(classes):
        unregister_class(cls)

if __name__ == "__main__":
    register()