### Special Symbols

IDL documentation uses the following symbolic notations:

[item] | Italic brackets surrounding an item indicate that the item is optional.
[item] | Brackets shown in regular typeface are a required part of the syntax.
item ... | Ellipsis points following an item indicate that the item may occur one or more times.
item , ... | If an item is followed by a literal punctuation character and then by ellipsis points, the item may occur either once without the punctuation character, or more than once with the punctuation character separating each instance.
... | If ellipsis points are shown on a line by themselves, the item or set of items in the preceding line may occur any number of additional times.
item | item | If several items are shown separated by vertical bars, exactly one of those items must occur.

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