microsoft colllinear points

from fractions import Fraction as fr
f=math.factorial
class Solution:
    def maxPoints(self, points: List[List[int]]) -> int:
        def ncr(n,r):
            return f(n)//f(r)//f(n-r)
        n=len(points)
        slope = lambda x1,y1,x2,y2:(y2-y1)/(x2-x1)
        d=defaultdict(set)
        ans=0
        if n==1:return 1
        for i in range(n):
            for j in range(i+1,n):
                x1,y1=points[i]
                x2,y2=points[j]
                if x1==x2:
                    d[(inf,x1)].update({i,j})
                else:
                    sp=fr(y2-y1,x2-x1)
                    incept=y1-sp*x1
                    d[(sp,incept)].update({i,j})
        ans=0
        for i in d.values():
            t=len(i)
            if t>=3:
                ans+=ncr(t,3)
        return ans