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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 _project_is_apache():
 """Determine if a project is Apache. Look for a key string in a set of possible license files to figure out if a project looks to be Apache. This is used as a precondition for enforcing license headers. """


    global _is_apache_cache
    if _is_apache_cache is not None:
        return _is_apache_cache
    license_files = ["LICENSE"]
    for filename in license_files:
        try:
            with open(filename, "r") as file:
                for line in file:
                    if re.search('Apache License', line):
                        _is_apache_cache = True
                        return True
        except IOError:
            pass
    _is_apache_cache = False
    return False