Checks through the previous_actions iterable if required actions have
        been executed

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