def forward(self, variables: List[Variable]) -> Variable:
        """
        Aggregates a list of variables.
        In TextGrad, forward pass of aggregation is simply concatenation of the values of the variables.
        The backward pass performs a reduction operation on the gradients of the variables.
        This reduction is currently an LLM call to summarize the gradients.

        :param variables: The list of variables to be aggregated.
        :type variables: List[Variable]
        :return: The aggregated variable.
        :rtype: Variable
        """
        concat_values = "\n".join([v.get_value() for v in variables])
        role_descriptions = set([v.get_role_description() for v in variables])
        role_descriptions = ", ".join(role_descriptions)
        
        # We create a unique meta tag that identifies which variables are aggregated together.
        # We also need to communicate to the variables that they are part of a mean operation.
        reduce_meta = {"op": _reduce_gradients_mean, "id": id(variables)}
        
        aggregated_variable = Variable(value=concat_values, 
                                    role_description=f"a combination of the following variables: {role_descriptions}.",
                                    predecessors=variables,
                                    requires_grad=any([v.requires_grad for v in variables]))
        
        aggregated_variable.set_grad_fn(BackwardContext(backward_fn=self.backward,
                                                        aggregated_variable=aggregated_variable))
        
        aggregated_variable._reduce_meta = [reduce_meta]
        return aggregated_variable

        Aggregates a list of variables.
        In TextGrad, forward pass of aggregation is simply concatenation of the values of the variables.
        The backward pass performs a reduction operation on the gradients of the variables.
        This reduction is currently an LLM call to summarize the gradients.

        :param variables: The list of variables to be aggregated.
        :type variables: List[Variable]
        :return: The aggregated variable.
        :rtype: Variable
        
textgrad/autograd/algebra.py