It is giving error that global name 'angle' is not defined

although I have already defined the variable 'angle'

```
class Triangle(object):
number_of_sides=3
def __init__(self,angle1,angle2,angle3):
self.angle1=angle1
self.angle2=angle2
self.angle3=angle3
def check_angles(self):
if self.angle1+self.angle2+self.angle3 == 180:
return True
else:
return False
my_triangle = Triangle(90,30,60)
class Equilateral(Triangle):
angle = 60
def __init__(self):
self.angle1=angle
self.angle2=angle
self.angle3=angle
tri= Equilateral()
print Equilateral.number_of_sides
print Equilateral.check_angles()
```