Define set type from all elements type (or empty_dict type).

def visit_Dict(self, node):
        """ Define set type from all elements type (or empty_dict type). """
        self.generic_visit(node)
        if node.keys:
            for key, value in zip(node.keys, node.values):
                value_type = self.result[value]
                self.combine(node, key,
                             unary_op=partial(self.builder.DictType,
                                              of_val=value_type))
        else:
            self.result[node] = self.builder.NamedType(
                "pythonic::types::empty_dict")