def region_2d_to_origin_3d(region: 'bpy.types.Region', rv3d:
    'bpy.types.RegionView3D', coord, clamp: float=None) ->'mathutils.Vector':
    """Return the 3d view origin from the region relative 2d coords. 

    :param region: region of the 3D viewport, typically bpy.context.region. 
    :type region: 'bpy.types.Region'
    :param rv3d: 3D region data, typically bpy.context.space_data.region_3d. 
    :type rv3d: 'bpy.types.RegionView3D'
    :param coord: 2d coordinates relative to the region; (event.mouse_region_x, event.mouse_region_y) for example. 
    :param clamp: Clamp the maximum far-clip value used. (negative value will move the offset away from the view_location) 
    :type clamp: float
    :return:  The origin of the viewpoint in 3d space. 
    """
    pass
