anchor.diff:  /// An error which is thrown when an object cannot be encoded.
   ///
   /// Example:
  +///
   ///     var encoder = new TomlEncoder();
   ///     encoder.encode({'a': null});
  +///
   /// throws an [UnknownValueTypeError] because `null` is not a valid TOML value.
   class UnknownValueTypeError {
   
  
positive.code: /// because it does not have a unique value type.
  ///
  /// Example:
  ///     var encoder = new TomlEncoder();
  ///     encoder.encode({'a': [1, '2']});
  /// throws an [MixedArrayTypesError] because `1` and `'2'` are of different
  /// types.
  class MixedArrayTypesError {
  
negative.code: /// string which cannot be represented by TOML.
  class InvalidStringError {
  
    /// A message which describes the error.
    final String msg;
  
    InvalidStringError(this.msg);
  