human
Solve in Python:
A transaction is possibly invalid if:

the amount exceeds $1000, or;
if it occurs within (and including) 60 minutes of another transaction with the same name in a different city.

Each transaction string transactions[i] consists of comma separated values representing the name, time (in minutes), amount, and city of the transaction.
Given a list of transactions, return a list of transactions that are possibly invalid.  You may return the answer in any order.
 
Example 1:
Input: transactions = ["alice,20,800,mtv","alice,50,100,beijing"]
Output: ["alice,20,800,mtv","alice,50,100,beijing"]
Explanation: The first transaction is invalid because the second transaction occurs within a difference of 60 minutes, have the same name and is in a different city. Similarly the second one is invalid too.
Example 2:
Input: transactions = ["alice,20,800,mtv","alice,50,1200,mtv"]
Output: ["alice,50,1200,mtv"]

Example 3:
Input: transactions = ["alice,20,800,mtv","bob,50,1200,mtv"]
Output: ["bob,50,1200,mtv"]

 
Constraints:

transactions.length <= 1000
Each transactions[i] takes the form "{name},{time},{amount},{city}"
Each {name} and {city} consist of lowercase English letters, and have lengths between 1 and 10.
Each {time} consist of digits, and represent an integer between 0 and 1000.
Each {amount} consist of digits, and represent an integer between 0 and 2000.

Give me a the Python code you requested?
assistant
#Here is the Python code you requested.

from collections import defaultdict
class Transaction:
    def __init__(self, name, time, amount, city):
        self.name = name
        self.time = int(time)
        self.amount = int(amount)
        self.city = city
    
class Solution:
    def invalidTransactions(self, transactions: List[str]) -> List[str]:
        invalid = []
        trans_index = defaultdict(list)
        trans = []
        for t in transactions:
            name, time, amount, city = t.split(',')
            trans.append(Transaction(name, time, amount, city))
        trans.sort(key = lambda x: x.time)
        
        s = set()
        for i in range(len(trans)):
            t1 = trans[i]
            if t1.amount > 1000:
                s.add(\"{},{},{},{}\".format(t1.name, t1.time, t1.amount, t1.city))
            for j in range(i + 1, len(trans)):
                t2 = trans[j]
                if t2.time - t2.time > 60:
                    break
                if t2.name == t1.name and t2.time - t1.time <= 60 and t1.city != t2.city:
                    s.add(\"{},{},{},{}\".format(t1.name, t1.time, t1.amount, t1.city))
                    s.add(\"{},{},{},{}\".format(t2.name, t2.time, t2.amount, t2.city))
        return list(s)