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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 cascaded_union(cls, vectors, dst_crs, prevalidate=False):
 # type: (list, CRS, bool) -> GeoVector """Generate a GeoVector from the cascade union of the impute vectors."""

        try:
            shapes = [geometry.get_shape(dst_crs) for geometry in vectors]

            if prevalidate:
                if not all([sh.is_valid for sh in shapes]):
                    warnings.warn(
                        "Some invalid shapes found, discarding them."
                    )

        except IndexError:
            crs = DEFAULT_CRS
            shapes = []

        return cls(
            cascaded_union([sh for sh in shapes if sh.is_valid]).simplify(0),
            crs=dst_crs
        )