import re


def process_replaces(pre_process_str, replaces):
    """
    Performs string replaces in the original ocr_result in the pre processing
    stage of the OCR result.

    Args:
        pre_process_str (str): OCR document str in the pre process stage;
        replaces (list): List of tuples in the following format:
                         [(regexp, replace_str), (regexp, replace_str), ...]

    Returns:
        (str): The pre processed OCR result string after the DRM option
               replaces.
    """
    for regexp, replacement in replaces:
        pre_process_str = re.sub(regexp, replacement, pre_process_str)

    return pre_process_str