@property
	def envelope(self):
		if not self.sender and not self.author:
			raise ValueError("Unable to determine message sender; no author or sender defined.")

		return self.sender or self.author[0]
Solve a Polynomial Risch Differential Equation with degree bound n.
dataset/ETHPy150Open marrow/mailer/marrow/mailer/message.py/Message.envelope--crossover with--dataset/ETHPy150Open sympy/sympy/sympy/integrals/rde.py/solve_poly_rde