code: def from_dynacRepr(cls, pynacRepr):
          
          cavID = int(pynacRepr[1][0][0])
          xesln = float(pynacRepr[1][1][0])
          phase = float(pynacRepr[1][1][1])
          fieldReduction = float(pynacRepr[1][1][2])
          isec = int(pynacRepr[1][1][3])
          return cls(phase, fieldReduction, cavID, xesln, isec)
docs: Construct a ``CavityAnalytic`` instance from the Pynac lattice element