要使用Amazon Textract提取键值对，您可以遵循以下步骤：

1. 设置Amazon Textract客户端：

import boto3

# 创建Textract客户端
textract_client = boto3.client('textract')

2. 调用StartDocumentTextDetection方法来开始文档文本检测：

response = textract_client.start_document_text_detection(
    DocumentLocation={
        'S3Object': {
            'Bucket': 'your-bucket-name',
            'Name': 'your-document-key'
        }
    }
)

# 获取文档检测作业ID
job_id = response['JobId']

3. 使用GetDocumentTextDetection方法获取文档检测结果：

response = textract_client.get_document_text_detection(JobId=job_id)

# 获取文档中的文本块
blocks = response['Blocks']

4. 遍历文本块并提取键值对：

key_value_pairs = []

for block in blocks:
    if block['BlockType'] == 'KEY_VALUE_SET':
        key_value_pair = {}

        for relationship in block['Relationships']:
            if relationship['Type'] == 'CHILD':
                for child_id in relationship['Ids']:
                    child_block = next(
                        child_block for child_block in blocks if child_block['Id'] == child_id
                    )

                    if child_block['BlockType'] == 'KEY':
                        key_value_pair['Key'] = child_block['Text']
                    elif child_block['BlockType'] == 'VALUE':
                        key_value_pair['Value'] = child_block['Text']

        key_value_pairs.append(key_value_pair)

完整代码示例：

import boto3

# 创建Textract客户端
textract_client = boto3.client('textract')

# 开始文档文本检测
response = textract_client.start_document_text_detection(
    DocumentLocation={
        'S3Object': {
            'Bucket': 'your-bucket-name',
            'Name': 'your-document-key'
        }
    }
)

# 获取文档检测作业ID
job_id = response['JobId']

# 获取文档检测结果
response = textract_client.get_document_text_detection(JobId=job_id)

# 获取文档中的文本块
blocks = response['Blocks']

# 提取键值对
key_value_pairs = []

for block in blocks:
    if block['BlockType'] == 'KEY_VALUE_SET':
        key_value_pair = {}

        for relationship in block['Relationships']:
            if relationship['Type'] == 'CHILD':
                for child_id in relationship['Ids']:
                    child_block = next(
                        child_block for child_block in blocks if child_block['Id'] == child_id
                    )

                    if child_block['BlockType'] == 'KEY':
                        key_value_pair['Key'] = child_block['Text']
                    elif child_block['BlockType'] == 'VALUE':
                        key_value_pair['Value'] = child_block['Text']

        key_value_pairs.append(key_value_pair)

# 打印键值对
for pair in key_value_pairs:
    print('Key:', pair['Key'])
    print('Value:', pair['Value'])
    print('---')

请注意，上述示例假设您已经设置了适当的AWS认证，并且将需要替换的参数（例如桶名和文档键）替换为您自己的值。