Adding doc_stride while preprocessing the data for Question Answering

[IamSparky]

I am trying to modify the following function for preprocessing a multilingual question answering dataset. Can someone please help me by letting me know on how to add the doc_stride while preprocessing the data as the contexts paragraphs are really long ! It seems really difficult to understand and implement all the concept all by my own. Early Thanks for showing support to this thread.

def process_data(context, question, answer, tokenizer, max_len):
    len_ans = len(answer)
    idx0 = None
    idx1 = None

    # we will try to get the start index and end index of answer in the question string:
    for index in (i for i, e in enumerate(question) if e == answer[0]):
        if question[index: index + len_ans] == answer:
            idx0 = index
            idex1 = index + len_ans - 1
            break
    
    # creating a vector to mark the indexes in context where answer is present with 1 and rest of the others will be 0
    char_targets = [0] * len(context)
    if idx0 is not None and idx1  is not None:
        for c in range(idx0, idx1 + 1):
            char_targets[c] = 1
        
    # tokenization of the context string
    tokenized_context = tokenizer.encode(context)
    original_context_input_ids = tokenized_context.ids[1:-1]
    context_offsets = tokenized_context.offsets[1:-1]

    # getting the offsets of the target index
    target_indexes = []
    for j, (offset1, offset2) in enumerate(context_offsets):
        if sum(context_offsets[offset1:offset2]) > 0:
            target_indexes.append(j)

    # start and end index of target
    targets_start = target_indexes[0]
    targets_end = target_indexes[-1]

    # tokenization of the question string
    tokenized_question = tokenizer.encode(question)
    original_question_input_ids = tokenized_question.ids[1:-1]
    question_offsets = tokenized_question.offsets[1:-1]

    input_ids = [101] + original_question_input_ids + [102] + original_context_input_ids + [102] # [101] & [102] is for CLS and SEP tokens
    token_type_ids = [0] * (len(original_question_input_ids) + 2) + [1] * (len(original_context_input_ids) + 1) # +2 is for CLS and SEP token and +1 for SEP token 
    mask = [1] * len(token_type_ids)
    actual_offsets = [(0, 0)] + question_offsets + [(0, 0)] + context_offsets + [(0, 0)] # [(0, 0)] is for CLS token offset at start and SEP token offset for the rest 
    targets_start += len([101] + original_question_input_ids + [102])
    targets_end += len([101] + original_question_input_ids + [102])

    # padding
    padding_length = max_len - len(input_ids)
    if padding_length > 0:
        input_ids = input_ids + ([0] * padding_length)
        mask = mask + ([0] * padding_length)
        token_type_ids = token_type_ids + ([0] * padding_length)
        tweet_offsets = tweet_offsets + ([(0, 0)] * padding_length)


    padding_length = max_len - len(input_ids)
    if padding_length > 0:
        input_ids = input_ids + ([0] * padding_length)
        mask = mask + ([0] * padding_length)
        token_type_ids = token_type_ids + ([0] * padding_length)
        tweet_offsets = tweet_offsets + ([(0, 0)] * padding_length)
    
    return {
        'context': context,
        'question': question,
        'answer': answer,
        'ids': input_ids,
        'mask': mask,
        'token_type_ids': token_type_ids,
        'targets_start': targets_start,
        'targets_end': targets_end,
        'offsets': tweet_offsets
    }