def prune(self, var, value, removals):
        "Rule out var=value."
        self.curr_domains[var].remove(value)
        if removals is not None: removals.append((var, value))
def prune(self, var, value, removals):
        "Rule out var=value."
        self.curr_domains[var].remove(value)
        if removals is not None: removals.append((var, value))
def prune ( self , var , value , removals ) : self . curr_domains [ var ] . remove ( value ) if removals is not None : removals . append ( ( var , value ) )
Rule out var=value.
Rule out var = value .