Interfere with ``not`` operation to :func:`numpy.logical_not`.

def visit_UnaryOp(self, node):
        """Interfere with ``not`` operation to :func:`numpy.logical_not`."""

        if isinstance(node.op, Not):
            self._debug('UnaryOp', node.op, incr=1)
            operand = self[node.operand]
            self._debug('|-', operand, incr=2)
            tn = self._tn()
            result = numpy.logical_not(operand)
            self._debug('|_', result, incr=2)
            self[tn] = result
            return ast_name(tn)
        else:
            return self.generic_visit(node)