How to create relations in owlready2 after the dynamic creation of the property?

Question

Using owlready2 I can create properties for my ontology, as below:

with onto:
    class Drug(Thing):
        pass
    class Ingredient(Thing):
        pass

relation_name = "has_for_ingredient"

with onto: 
   NewProperty = types.new_class(relation_name, (ObjectProperty, FunctionalProperty))
   NewProperty.domain = domain
   NewProperty.range = range

I can see them using list(onto.properties()). Now I want to create relations using the code below (in my actual code this will be done dynamically):

my_drug = Drug("my_drug")
acetaminophen = Ingredient("acetaminophen")
my_drug.has_for_ingredient = [acetaminophen]

but I get the error:

AttributeError: 'list' object has no attribute 'storid'

I have also tried to create the property using only ObjectProperty, without FunctionalProperty, but get the error:

AttributeError: 'int' object has no attribute 'namespace'

Using the documentation I could not figure what is the issue... And also, what is the meaning of using the FunctionalProperty?

Answer 1

with onto: 
   NewProperty = types.new_class(relation_name, (ObjectProperty, ))
   NewProperty.domain = [Drug]
   NewProperty.range = [Ingredient]

was the way to go. Whereas:

with onto: 
   NewProperty = types.new_class(relation_name, (ObjectProperty))
   ...

thorws the AttributeError: 'list' object has no attribute 'storid'

Apparently a tuple is required to create the property dynamically.