import re


def remove_blank(text):
    """
    Args:
        text (str): input text, contains blank between zh and en, zh and zh, en and en
    Returns:
        str: text without blank between zh and en, zh and zh, but keep en and en

    Examples:
        >>> text = "比如 Convolutional Neural Network，CNN 对应中 文是卷 积神 经网络。"
        >>> remove_blank(text)
        "比如Convolutional Neural Network，CNN对应中文是卷积神经网络。"
    """
    # filter blank space between Chinese characters
    text = re.sub(r'([^a-zA-Z])([\u0020]*)', r'\1', text)
    # remove blank space between English characters and Chinese characters
    text = re.sub(r'([\u0020]*)([^a-zA-Z])', r'\2', text)
    return text