How to use ValidateScript on a collection instead of the elements in the collection?

Microsoft docs mention that if I apply the ValidateScript attribute to a collection, it will evaluate each element of the collection:

If this attribute is applied to a collection, each element in the collection must match the pattern.

I am trying to validate the collection itself. For example its type:

function testme {
    param(
        [ValidateScript({$_ -is [array] -or $_ -is [hashtable]}, ErrorMessage = "The item '{0}' did not pass validation of script '{1}'")]
        [psobject]$args
    )
}

$arr = [psobject]@("aaa", "bbb")
$arr -is [array] #returns True 
testme -args $arr

This - as expected - nets me this result: Cannot validate argument on parameter 'args'. The item 'aaa' did not pass validation of script '$_ -is [array] -or $_ -is [hashtable]'

I am not able to figure out how to match the input collection instead of the elements in the collection.

ValidateScript derives from ValidateEnumeratedArgumentsAttribute, as it name hints, arguments are enumerated and validated. If you want to validate a collection as a whole you'd need to go one level up and derive from ValidateArgumentsAttribute however, there isn't a PowerShell built-in attribute decoration for this, you'd need to implement it yourself, here is a little example:

using namespace System.Management.Automation

class ValidateCollection : ValidateArgumentsAttribute {
    [void] Validate([Object] $arguments, [EngineIntrinsics] $engineIntrinsics) {
        # perhaps `$arguments -is [ICollection]` might do here
        if ($arguments -is [array] -or $arguments -is [hashtable]) {
            return
        }

        throw [MetadataException]::new(
            "The item '$arguments' of type '$($arguments.GetType())' did not pass validation.")
    }
}

Then for the usage you decorate your parameter like so:

function testme {
    param(
        [ValidateCollection()]
        [psobject] $MyParameter
    )
}

testme 1, 2, 3, 4       # passes test
testme @{ foo = 'bar' } # passes test
testme 1                # fails