$data = [
"product" => [
"sku"=> $productsku,
// "attribute_set_id"=> 4,
//"attribute_set_id" => $mage_attr_set_id,
// "entity_type_id" => $entity_type_id,
"visibility" => 2,
// "custom_attributes" => $subArray
"custom_attributes" => [
[
"attribute_code" => "selling_unit_of_measure",
"value" => "each"
]
]
]
];