Suppose I have a universe selection that runs on Midnight on Fridays, and some equities are removed from my universe. Subsequently, I use a Liquidate call to remove them in my Execute class. For US equities, those calls happen outside of market hours. Do the Liquidate orders get converted to On Market Orders for the next Monday (except for holidays, etc.)? 

If there are no holdings for the equity in question, I presume the call is a no-op. Is that a good assumption?

This is the method I am using in my execution model:

class OrderExecution(ExecutionModel):
	...
    def OnSecuritiesChanged(self, algorithm, changes):
        # Event handler for securities added and removed.
        # changes.AddedSecurities:
        #   We do not need to do anything for AddedSecurities.
        # changes.RemovedSecurities:
        #   Liquidate removed securities.
        for removed in changes.RemovedSecurities:
            algorithm.Log("Liquidating removed security {}".format(removed.Symbol.Value))
            algorithm.Liquidate(removed.Symbol)
            algorithm.Log("Available cash now ${:.2f}".format(algorithm.Portfolio.Cash))

Thank you for your help.