Hello everyone . I was getting my hands on Python to learn Data structures and algorithms in python. I tried to implement progression class with sub classes : AP , GP and fibonacci… the implementation of AP and GP works well but fibonacci doesnt work right. Here is the code:

```
class progression:
def __init__(self,start):
self.start = start
self.x = str()
self.answer = int()
def __next__(self):
self.answer = self.start
self.start += 1
return self.answer
def __iter__(self):
return self
def printer(self,n):
for i in range(0,n):
self.x = self.x + ' ' + ''.join(str(next(self)))
print(self.x)
class arithematic(progression):
def __init__(self,start,inc):
super().__init__(start)
self.inc = inc
def __next__(self):
self.answer = self.start
self.start += self.inc
return self.answer
class gp(progression):
def __init__(self,start,factor):
super().__init__(start)
self.factor = factor
def __next__(self):
self.answer = self.start
self.start *= self.factor
return self.answer
class fibo(progression):
def __init__(self,first,second):
super().__init__(first)
self.prev = second - first
def next(self):
self.answer = self.start
self.start += self.prev
self.prev = self.answer
return self.answer
obj = fibo(1,3)
obj.printer(10)
```

Help me debug the program please! i cannot seem to find the error