@classmethod
def from_dynacRepr(cls, pynacRepr):
    """
        Construct a ``CavityAnalytic`` instance from the Pynac lattice element
        """
    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)
