// Utility translator method for lambda expressions that are part of group by. Given a lambda expression and its translated
// inputs, translates the lambda expression, assuming the input needs to be used as a grouping input
private DbExpression TranslateLambda(LambdaExpression lambda, DbExpression input, out DbGroupExpressionBinding binding)
{
input = NormalizeSetSource(input);
// create binding context for this lambda expression
var alias = _aliasGenerator.Next();
binding = input.GroupBindAs(alias, string.Format(CultureInfo.InvariantCulture, "Group{0}", alias));
return TranslateLambda(lambda, binding.Variable);
}