code: def set(property_path, value)
        if property_path
          last_node = @config
          last_name = property_path.split('.').inject(nil) do |name, section|
            last_node = last_node[name] ||= {} unless name.nil?
            section.to_sym
          end
          last_node[last_name] = value
        end
        return nil
      end
docs: Writes a new value to a property or category in memory (creating it if
   necessary).
   They can be indexed using a dot-based notation (e.g. "category.property"
   to access "property" under "category").