def initialize_labels(self, expr, node, depgraph, unique_index):
        if isinstance(expr, linearlogic.AtomicExpression):
            name = self.find_label_name(expr.name.lower(), node, depgraph, unique_index)
            if name[0].isupper():
                return linearlogic.VariableExpression(name)
            else:
                return linearlogic.ConstantExpression(name)
        else:
            return linearlogic.ImpExpression(
                       self.initialize_labels(expr.antecedent, node, depgraph, unique_index),
                       self.initialize_labels(expr.consequent, node, depgraph, unique_index))