Killed process ubuntu

I ran my script for annotating images before 3 days and when it was finish yesterday, this message shows up "Killed". Why is that?

And when I run dmesg, the output is: [269538.495694] Out of memory: Killed process 10231 (python3) total-vm:5864124kB, anon-rss:4250068kB, file-rss:4kB, shmem-rss:0kB, UID:1000 pgtables:8880kB oom_score_adj:0

I'm using ubuntu 22.04.

The script opens json file on the beggining and inside some function for annotating text on images, the write_json() is called. And the data (images with text) was read from .h5 file

def write_json(data, filename='da.json'):
    with open(filename,'w') as file:
          ujson.dump(data,file,indent=4)
    
with open("da.json") as json_file:
     data=ujson.load(json_file)
     temp=data["annotations"]

def viz_textbb(text_im, imageName, charBB_list, wordBB, textToList, alpha=1.0):
    start = 0
    coordinate = []
    name = []
    upperList = []
    downList = [] 
    FinalFinal = [] 
    imageData = { }
    dictList = []

  for eachWord in textToList:
        length = len(eachWord)
        for i in range(0,4):
            for j in range(start,length+start):
                coordinate.append([charBB_list[0][0][i][j], charBB_list[0][1][i][j]])
            name.append(coordinate)
            coordinate = []

         for j in range(0, length):
            for i in range(len(name)) :
                if(i == 0 or i == 1):
                    upperList.append(name[i][j])
                if(i == 2):
                    downList.append(name[i+1][j])
                if(i == 3):
                    downList.append(name[i-1][j])

         down = reversed(downList)
         joinList = [*upperList,*down,upperList[0]]

         FinalFinal.append(joinList)
        
         imageData['transcription']=eachWord
         imageData['language']="Latin"
         imageData['illegibility']=False
         imageData['points']=joinList
         dictionary_copy = imageData.copy()
         dictList.append(dictionary_copy)

         del(dictionary_copy)

         name=[]
         upperList = []
         downList = []
         start = len(eachWord) + start

  finalDict = {f'gt_{imageName}':dictList}
  
  temp.update(finalDict)
        
  write_json(data)

def main(db_fname):
    db = h5py.File(db_fname, 'r')
    dsets = sorted(db['data'].keys())
    #print ("total number of images : ", colorize(Color.RED, len(dsets), highlight=True))
    for k in dsets:
        rgb = db['data'][k][...]
        charBB = db['data'][k].attrs['charBB']
        wordBB = db['data'][k].attrs['wordBB']
        txt = db['data'][k].attrs['txt']
        textToList = (db['data'][k].attrs['txt']).tolist()
        
        viz_textbb(rgb, k,[charBB], wordBB, textToList)
        
        print ("image name        : ", colorize(Color.RED, k, bold=True))
        # print ("  ** no. of chars : ", colorize(Color.YELLOW, charBB.shape[-1]))
        # print ("  ** no. of words : ", colorize(Color.YELLOW, wordBB.shape[-1]))
        print ("  ** text         : ", colorize(Color.GREEN, txt))
        
    db.close()
json.close()

if __name__=='__main__':
    main('results/SynthText.h5')