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@triblondon Comments?

I've tested and this looks good.
It depends on the definition of this function.  We can handle that case but is the developer then missing the point of these chained functions?  The function should return an array of polyfill identifier names expanded from the polyfill identifier name.  If the expansion can not occur you should not expand and return the argument, or at the very least return a base case explicitly.  

In this case relying on `configuredAliases[polyfillIdentifierName]` to be undefined when expansion can not occur and catching that one layer above is too much obfuscation for me.