my_class.yml

parameters:
  default_name:
    first_name: ''
    middle_name: ''
    last_name: ''
  something:
     ${default_name}
     first_name: 'for'
     last_name: 'ever'

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node should have the following parameters then:
parameters:
    default_name:
        first_name: ''
        middle_name: ''
        last_name: ''
    something:
        first_name: 'for'
        middle_name: ''
        last_name: 'ever'