Default attributes from yaml file is not working

[imadbourouche]

When defining default values for attributes in a yaml file like this

acronym:
  display: "general" 
  label: "Acronym"
  helpText: "The Acronym of the catalog which is described by these metadata."
  example: 'agroportal'
  default: 'ontoportal'

and defining the attribute in the model

model :SemanticArtefactCatalog, namespace: :mod, scheme: File.join(__dir__, '../../../../config/schemes/semantic_artefact_catalog.yml'),
                                                            name_with: ->(s) { RDF::URI.new(LinkedData.settings.id_url_prefix) }

attribute :acronym, namespace: :omv, enforce: [:unique]

When we call save method to save the mode in triple store we will have this error

NoMethodError: undefined method `call' for "ontoportal":String
    /home/bourouch/work/MOD-API/goo/lib/goo/base/resource.rb:258:in `block in save'
    /home/bourouch/work/MOD-API/goo/lib/goo/base/resource.rb:255:in `each'
    /home/bourouch/work/MOD-API/goo/lib/goo/base/resource.rb:255:in `save'
    /home/bourouch/work/MOD-API/ontologies_linked_data/lib/ontologies_linked_data/models/base.rb:13:in `save'
    /home/bourouch/work/MOD-API/ontologies_linked_data/test/models/mod/test_artefact_catalog.rb:11:in `test_create_artefact_catalog'