Python中的“Self”对象是什么？

>>> class Ancestor( object ):
    def __init__( self ):
        self.name = "Ancestor"
    def getName( self ):
        return self.name


>>> class Base1( Ancestor ):
    def __init__( self ):
        self.name = "Base1"
        super( Base1,self ).__init__( )
    def getName( self ):
        return self.name


>>> class Base2( Base1 ):
    def __init__( self ):
        self.name = "Base2"
        super( Base2,self ).__init__( )
    def getName( self ):
        return self.name
    def getB1Name( self ):
        return super( Base2,self ).getName( )


>>> b2 = Base2( )
>>> b2.getName( )
'Ancestor'
>>> b2.getB1Name( )
'Ancestor'

我无法理解结果.我期待b2.getName()的结果为“Base2”,b2.getB1Name()的结果为“Base1”