code: function toSource(func){
    if (func != null){
      try {
        return funcToString.call(func)
      } catch (e){}
      try {
        return String(func)
      } catch (e){}
    }
  
    return ''
  }
docs: Converts `func` to its source code.
  
  @private
  @param {Function} func The function to process.
  @returns {string} Returns the source code.