Construct a ``Quad`` instance from the Pynac lattice element

def from_dynacRepr(cls, pynacRepr):
        """
        Construct a ``Quad`` instance from the Pynac lattice element
        """
        L = float(pynacRepr[1][0][0])
        B = float(pynacRepr[1][0][1])
        aperRadius = float(pynacRepr[1][0][2])
        return cls(L, B, aperRadius)