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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 find_store_dirs(cls):
 """ Returns the primary package directory and any additional ones from QUILT_PACKAGE_DIRS. """

        store_dirs = [default_store_location()]
        extra_dirs_str = os.getenv('QUILT_PACKAGE_DIRS')
        if extra_dirs_str:
            store_dirs.extend(extra_dirs_str.split(':'))
        return store_dirs