ExtractSchema() does not consider or type

[psmolinsky]

Description
Schema.ExtractSchema() method consider the or type to be as same as the pair type. This make them indistinguishable.

Steps To Reproduce

1. Create a Schema with Michelson containing the or type and call the method.

const schema = new Schema({
    prim: 'or',
    args: [
        { prim: 'string' },
        { prim: 'nat' },
    ],
});

const extracted = schema.ExtractSchema();

2. Returned value in extracted variable is:

{
    '0': 'string',
    '1': 'nat',
}

3. Do the same with similar schema using the pair type:

const schema = new Schema({
    prim: 'pair',
    args: [
        { prim: 'string' },
        { prim: 'nat' },
    ],
});

const extracted = schema.ExtractSchema();

4. It returns the same result:

{
    '0': 'string',
    '1': 'nat',
}

Expected behavior

The or type should be expressed in the extracted schema. For example:

{
    or: [
        'string',
        'nat',
    ],
}

[psmolinsky]

One more remarks: What if the schema is ambiguous? Even without annotations. Please consider it...

const fooSchema = {
    prim: 'or',
    args: [
        { prim: 'int', annots: ['%add'] },
        { prim: 'int', annots: ['%remove'] },
    ],
}