incorrect getDataSetIndexByLabel function

internal func getDataSetIndexByLabel(_ label: String, ignorecase: Bool) -> Int
{
// TODO: Return nil instead of -1
if ignorecase
{
return dataSets.firstIndex {
guard let label = $0.label else { return false }
return label.caseInsensitiveCompare(label) == .orderedSame
} ?? -1
}
else
{
return dataSets.firstIndex { $0.label == label }
?? -1
}
}
label.caseInsensitiveCompare(label) == .orderedSame is always return true，The let label name is the same as the parameter name