encoder method
Encodes a value to a String.
Uses the provided encoder if available, otherwise uses Utils.encode.
Implementation
String encoder(dynamic value, {Encoding? charset, Format? format}) =>
    _encoder?.call(
      value,
      charset: charset ?? this.charset,
      format: format ?? this.format,
    ) ??
    Utils.encode(
      value,
      charset: charset ?? this.charset,
      format: format ?? this.format,
    );