define_default_attribute

# File activemodel/lib/active_model/attributes.rb, line 62
        def define_default_attribute(name, value, type)
          self._default_attributes = _default_attributes.deep_dup
          if value == NO_DEFAULT_PROVIDED
            default_attribute = _default_attributes[name].with_type(type)
          else
            default_attribute = Attribute::UserProvidedDefault.new(
              name,
              value,
              type,
              _default_attributes.fetch(name.to_s) { nil },
            )
          end
          _default_attributes[name] = default_attribute
        end