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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def is_valid(self, context):
 """Checks through the previous_actions iterable if required actions have been executed """

        if self.requires:
            for r in self.requires:
                if not r in context.executed_actions:
                    raise RequirementMissingError("Action '%s' requires '%s'" % (self.name, r))
        return True