This pattern is required to either NOT be present, which means the
master pattern is used to match, or it has a list of patterns to use
beneath the master maildir to match against.
This function checks to ensure that if patterns is not empty, ONLY
then is the `Pattern` keyword printed. Otherwise, there are many, many
problems.
If there IS a list of patterns, then we use proper escaping methods to
ensure that the exact string is constructed.
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