class_docstr: A class for representing multivariate polynomial rings. 
code: def __hash__(self):
      return hash(
          (
              self.__class__.__name__,
              self.dtype.ring,
              self.domain,
              self.symbols,
          )
      )
  
imports: from sympy.polys.domains.ring import Ring
  from sympy.polys.domains.compositedomain import CompositeDomain
  from sympy.polys.polyerrors import CoercionFailed, GeneratorsError
  from sympy.utilities import public
label_desc: Use image node_id 7 for calling the PolynomialRing obj's underlying member method code with example usage: obj.__hash__() and returns: hash