how to create raster transform json object in geometric raster function

[pingliu]

{
"raster_function":{"type":"Geometric_function"},
"raster_function_arguments":
{
"raster_transform":{"raster_transform":"Raster Transform JSON object","type":"Raster_function_variable"},
"z_offset":{"double":0,"type":"Raster_function_variable"},
"z_factor":{"double":1,"type":"Raster_function_variable"},
"raster":{"is_raster":true,"name":"raster","type":"Raster_function_variable"},
"type":"Raster_function_arguments"
},
"type":"Raster_function_template"
}

I can't find any sample for Raster Transform JSON object, could you help me?