sequence {
            analysisSession.useSitePackageProvider.getSubPackageFqNames(fqName, analysisSession.targetPlatform, nameFilter).forEach {
                yield(analysisSession.firSymbolBuilder.createPackageSymbol(fqName.child(it)))
            }
        }
    }

                    if (seenTopLevelPackages.add(packageName) && nameFilter(packageName)) {
                        yield(analysisSession.firSymbolBuilder.createPackageSymbol(FqName.ROOT.child(packageName)))
                    }
                }
            }
        }
    }

    override fun getPossibleCallableNames(): Set<Name> = withValidityAssertion {

        val exists = packageProvider.doesPackageExist(packageFqName, analysisSession.targetPlatform)
        if (!exists) {
            return null
        }
        return createPackageSymbol(packageFqName)
    }

    fun createPackageSymbol(packageFqName: FqName): KtFirPackageSymbol {
        return KtFirPackageSymbol(packageFqName, project, token)
    }

    inner class ClassifierSymbolBuilder {