human
Can you provide a the Python program you requested given the following:
Solve in Python:
At a lemonade stand, each lemonade costs $5. 
Customers are standing in a queue to buy from you, and order one at a time (in the order specified by bills).
Each customer will only buy one lemonade and pay with either a $5, $10, or $20 bill.  You must provide the correct change to each customer, so that the net transaction is that the customer pays $5.
Note that you don't have any change in hand at first.
Return true if and only if you can provide every customer with correct change.
 

Example 1:
Input: [5,5,5,10,20]
Output: true
Explanation: 
From the first 3 customers, we collect three $5 bills in order.
From the fourth customer, we collect a $10 bill and give back a $5.
From the fifth customer, we give a $10 bill and a $5 bill.
Since all customers got correct change, we output true.

Example 2:
Input: [5,5,10]
Output: true

Example 3:
Input: [10,10]
Output: false

Example 4:
Input: [5,5,10,10,20]
Output: false
Explanation: 
From the first two customers in order, we collect two $5 bills.
For the next two customers in order, we collect a $10 bill and give back a $5 bill.
For the last customer, we can't give change of $15 back because we only have two $10 bills.
Since not every customer received correct change, the answer is false.

 
Note:

0 <= bills.length <= 10000
bills[i] will be either 5, 10, or 20.
assistant
#Here is the Python program you requested.

class Solution:
    def lemonadeChange(self, bills: List[int]) -> bool:
        cash = {20: 0,
                10: 0,
                 5: 0}
        for paid in bills:
            refund = paid - 5
            if refund == 0:
                cash[5] += 1
                continue
            flag = False
            for note in cash:
                if cash[note]>= refund//note:
                    cash[note] -= refund // note
                    refund -= (refund// note) *note
                    flag = True
            if not flag or refund>0:
                return False
            cash[paid] += 1
        return True