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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 env(self):
 """The execution context for rowprocessors and row-generating notebooks and functions. """

        from copy import copy

        env = copy(self.doc.env)

        assert env is not None, 'Got a null execution context'

        env.update(self._envvar_env)

        env.update(self.all_props)

        return env