code: def get_context(self, arr, expr, context):
          
  
          expression_names = [x for x in self.get_expression_names(expr) if x not in set(context.keys()).union(['i'])]
  
          if len(expression_names) != 1:
              raise ValueError('The expression must have exactly one variable.')
  
          return {expression_names[0]: arr}
docs: Returns a context dictionary for use in evaluating the expression.
  
          :param arr: The input array.
          :param expr: The input expression.
          :param context: Evaluation context.