def encode_with(coder)
      super

      coder['source'] = source
      coder['dependency_digest'] = dependency_digest

      coder['required_paths'] = required_assets.map { |a|
        relativize_root_path(a.pathname).to_s
      }
      coder['dependency_paths'] = dependency_paths.map { |d|
        { 'path' => relativize_root_path(d.pathname).to_s,
          'mtime' => d.mtime.iso8601,
          'digest' => d.digest }
      }
    end
def encode_with(coder)
      super

      coder['source'] = source
      coder['dependency_digest'] = dependency_digest

      coder['required_paths'] = required_assets.map { |a|
        relativize_root_path(a.pathname).to_s
      }
      coder['dependency_paths'] = dependency_paths.map { |d|
        { 'path' => relativize_root_path(d.pathname).to_s,
          'mtime' => d.mtime.iso8601,
          'digest' => d.digest }
      }
    end
Serialize custom attributes.