class
StackB
(
____________________
/
____________________
)
:
def_init
(
self
)
:
____________________
(
)
.
____________________
(
)
def
pushBottom
(
self
,
e
)
:
self
.
____________________
(
____________________
)
def
push
(
self
,
e
)
:
self
.
____________________
(
____________________
)
def
pop
(
self
)
:
if
not
self
.
____________________
(
)
:
return
(
self
.
____________________
(
self
.
____________________
(
)
)
)
#o
no
definir
ya
que
se
hereda
def
____________________
(
self
)
:
return
____________________
(
)
.
____________________
(
)
