$declaresequence

From Valve Developer Community

Forward declares a sequence.

This is useful when you want to add other sequences as layers that aren't locally declared, such as when they're actually part of an external .mdl file (see $includemodel). $declaresequence makes a empty sequence entry so that the local sequence pointers can get set, and at run time these references are overwritten with the actual sequence index.

Syntax

$declaresequence (name)