xsd ,xsi parameters with Loopback

[Besbes Nesrine]

I have a service that has the schema 
<actionA xmlns:xsi="xsi URL " xmlns:xsd=" xsd URL"> 

<a xsd:type="xsd:string">A</a> 

<b xsd:type="xsd:string">B</b> 

<c xsd:type="xsd:string">C</c> 

</actionA>




so, with loopback 3 when I add the "xsd URL" on all the params, it works.
for example for the parameter "a":
a:{$attributes: { $xsiType: "{URL xsd}xsd:string", }, $value: "A", }

The loopback generate automatically "xsi URL" and the XML request will be as following:
<actionA> <a:Valeur xmlns:xsi="URL xsi" xmlns:xsd="URL xsd" xsi:type="xsd:string">A<a/> </actionA>

How can I generate "xsi URL" and "xsd URL" only in the header an not in params through loopback, to get an xml request similar to the service schema ?