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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def read_version(path):
 """Attempts to read a python version string from a runtime.txt file :param path: to source of the string :return: python version :rtype: unicode or None """

    version = None
    if os.path.exists(path):
        version = open(path, 'r', encoding='utf-8').read().strip()

    if version:
        return re.sub(r'^python-', '', version)

    return version