问当我运行以下python脚本时，未定义名称'collection'怎么办？

EN

import pymongo

from pymongo import MongoClient

from collections import defaultdict

client=MongoClient()

db=client.solarsystem

data=db.sun

query={

  "authors":{"$exists":True}

}

projection={

  "authors":[]

}

rm=list(collection.find(query,projection))

x=[y['authors']for y in rm]

d=defaultdict(list)

authors=[]

for i in x:

  for k in i:

    if k not in authors:

      authors.append(k)

for i in x:
  for k in i:
    for name in i:
      if name not in d[k]:
        d[k].append(name)

deg=defaultdict(int)

for x in authors:

  deg[x]=len(d[x])-1

print(deg)