Function 'Type' in custom output

Hey guys, I'm designing a process model where I need to convert a record with start date, and end date, into multiple records, with just delivery date. All the 3 fields are in the CDT. However, the process is failing on the node where I make the conversion through the following expression:

a!forEach(
items: pv!PODates,
expression: cast(
typeof(
'type{urn:com:appian:types:SP}SP_PurchaseOrder'()
),
'type!{urn:com:appian:types:SP}SP_PurchaseOrder'(
articleCode: pv!SP_PurchaseOrder.articleCode,
description: pv!SP_PurchaseOrder.description,
...

...

...
company: pv!SP_PurchaseOrder.company,
currency: pv!SP_PurchaseOrder.currency,
researchCertificates: pv!SP_PurchaseOrder.researchCertificates
)
)
)

And the error is allways: 

" (Expression evaluation error at function a!forEach: Error in a!forEach() expression during iteration 1: Expression evaluation error at function 'type{urn:com:appian:types:SP}SP_PurchaseOrder' [line 2]: The function 'type{urn:com:appian:types:sp}sp_purchaseorder' is unavailable.) (Data Outputs)"

Any tips, on what is causing this, or how to work around it?

Thanks in advance, Guys!!