appendStage
Append a pipeline stage to the mangled name using its index in the pipeline.
Appends "pipeline[idx]($stage)" to the mangled name.
Return
this
Parameters
idx
The index of the stage within the pipeline.
stage
The stage in the idx position of pipeline.
Throws
if:
The builder is not empty, and the previous token is not a stage type, index, or nested pipeline identifier
The builder has transitioned into stage component context.