def underscore(value)
      case value
      when Hash then value.deep_transform_keys! { |key| underscore(key) }
      when Symbol then underscore(value.to_s).to_sym
      when String then StringSupport.underscore(value)
      else value
      end
    end
def underscore(value)
      case value
      when Hash then value.deep_transform_keys! { |key| underscore(key) }
      when Symbol then underscore(value.to_s).to_sym
      when String then StringSupport.underscore(value)
      else value
      end
    end
Transforms values to underscore_case.
 This is the default case for deserialization in the JsonApi adapter.

 @example:
    "some-key" => "some_key",