certificate_import_from_pem seems to upload to /Common regardless of cert_ids field

using IControl ruby gem

f5.Management.KeyCertificate.certificate_import_from_pem(
    mode: 'MANAGEMENT_MODE_DEFAULT',
    cert_ids: { item: ["/Foo/testcert"] },
    pem_data: { item: [CERT_PEM] },
    overwrite: true
)

seems to upload testcert to the partition /Common, despite specifying the cert to be uploaded to /Foo, is there a way to get this to upload to /Foo?

F5 version: BIG-IP 12.1.0 Build 0.0.1434 Final