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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 _parseAtFrame(self, src):
 """ XXX Proprietary for PDF """

        src = src[len('@frame '):].lstrip()
        box, src = self._getIdent(src)
        src, properties = self._parseDeclarationGroup(src.lstrip())
        result = [self.cssBuilder.atFrame(box, properties)]
        return src.lstrip(), result