How to generate type list of lists?

Question

Java

I want to generate a field with type List<List<String>>
Tried like this

<xs:element name="splitContours" type="ns1:contourGroup" maxOccurs="unbounded"/>

<xs:complexType name="contourGroup">
    <xs:annotation>
        <xs:documentation>Группа контуров</xs:documentation>
    </xs:annotation>
    <xs:sequence>
        <xs:element name="contours" type="xs:string" maxOccurs="unbounded">
            <xs:annotation>
                <xs:documentation>Контуры</xs:documentation>
            </xs:annotation>
        </xs:element>
    </xs:sequence>
</xs:complexType>

But it turns out, an array of objects with the contours field, from which I already get an array of strings. A search for this type of information turned up nothing. Is it even possible to describe multidimensional arrays in xsd?