code python：'str'对象没有属性'decode'

Question

这是我的代码：

class FileReader(object):
    def __init__(self, filePath, encoder = None):
        self.filePath = filePath
        self.encoder = encoder if encoder != None else 'utf-8'

    def read(self):
        with open(self.filePath) as f:
            s = f.read()
        return s

    def content(self):
        s = self.read()
        return s.decode(self.encoder)

错误：属性：'str'对象没有属性'decode'我该如何解决？