计算一个顺序串中最大字符出现的次数

属于Python数据结构的问题，真的想了好久想不出来，希望各位帮帮忙（我是Python初学者）
要用到SqString顺序串的知识谢谢！！

采纳一下呗，谢谢！

MaxSize = 100
class SqString():
    def __init__(self,size=0):
        self.data = [None]*MaxSize
        self.size = 0
    def StrAssign(self,str):                  #  创建串
        for i,item in enumerate(str):
            self.data[i] = item
            self.size += 1
    def DispStr(self):                      # 输出串
        if self.size == 0:
            raise ValueError("str is empty")
        for i, item in enumerate(self.data):
            if item is None:
                break
            else:
                print(item, end = '')
    def getsize(self,str):           # 输出串s的长度
        print(self.size)
    
    def maxstr(self, str):
        maxstr = str[0]
        count = {}
        for i in str:
            if ord(i) > ord(maxstr):
                maxstr = i
        count[maxstr] = 0
        for i in str:
            if i == maxstr:
                count[maxstr] += 1
        return count


if __name__=='__main__':
   s_1 = "abcdzefghfazefgzazhiajzkzlmn"
   s1 = SqString()
   s1.StrAssign(s_1)
   print(s1.maxstr(s_1))

b = []
for i in str:
  a = str.count(i)
  b.append(a)
print(”出现最多的是:{}, {}次“.format(str[max(b)], max(b)))

你需要先解释 什么叫 顺序串，什么叫最大字符。