Create new unit with a function

[apkowalewski0]

I have been able to add in several new units by going into the derived_unit.yaml adding them directly into it. I need to add a unit that is converted by adding a constant. I want to have psia = psig + 14.696. I have created psig based on the [psi] unit and it works. When I try to convert psig to psia I get the following:

2.3.4 :007 > p = Unitwise(10, 'psig')
 => #<Unitwise::Measurement value=10 unit=psig>
2.3.4 :008 > p.convert_to('psia')
=> #<Unitwise::Measurement value=68947587.627683613367226734453442213195477645 unit=psia>

the definitition for psia and psig in derived_unit.yaml is

- :names: psig
  :symbol: psig
  :primary_code: psig
  :secondary_code: psig
  :scale:
    :value: 1.0
    :unit_code: "[psi]"
  :classification: misc
  :property: pressure
  :metric: false
  :special: false
  :arbitrary: false

- :names: psia
  :symbol: psia
  :primary_code: psia
  :secondary_code: psia
  :scale:
    :value: 1.0
    :unit_code: "psig"
    :function_code: psia
  :classification: misc
  :property: pressure
  :metric: false
  :special: true
  :arbitrary: false

and my functions in functional.rb are

  def self.to_psia(x)
      x + 14.696
    end`

   def self.from_psia(x)
      x - 14.696
    end

Is there something else that I need to add in to make sure that it is using the function properly? Or can you not add units that require functions?