def location_3d_to_region_2d(region: 'bpy.types.Region', rv3d:
    'bpy.types.RegionView3D', coord, default=None) ->'mathutils.Vector':
    """Return the region relative 2d location of a 3d position. 

    :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: 3d worldspace location. 
    :param default: Return this value if coord is behind the origin of a perspective view. 
    :return:  2d location 
    """
    pass
