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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 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)