ROOT (token: short_text [lag_newlines/spaces] {pos_id})     
 °--expr: {
    [0/0] {1}                                  
     ¦--'{': { [0/9] {2}                                    
     ¦--expr: {1 +  [1/0] {3}                               
     ¦   ¦--'{': { [0/0] {4}                                
     ¦   ¦--expr: 1 + 3 [0/0] {5}                           
     ¦   ¦   ¦--expr: 1 [0/1] {7}                           
     ¦   ¦   ¦   °--NUM_CONST: 1 [0/0] {6}                  
     ¦   ¦   ¦--'+': + [0/1] {8}                            
     ¦   ¦   °--expr: 3 [0/0] {10}                          
     ¦   ¦       °--NUM_CONST: 3 [0/0] {9}                  
     ¦   °--'}': } [0/0] {11}                               
     ¦--expr: {2 +  [1/6] {12}                              
     ¦   ¦--'{': { [0/0] {13}                               
     ¦   ¦--expr: 2 + s [0/0] {14}                          
     ¦   ¦   ¦--expr: 2 [0/1] {16}                          
     ¦   ¦   ¦   °--NUM_CONST: 2 [0/0] {15}                 
     ¦   ¦   ¦--'+': + [0/1] {17}                           
     ¦   ¦   °--expr: sin(p [0/0] {18}                      
     ¦   ¦       ¦--expr: sin [0/0] {20}                    
     ¦   ¦       ¦   °--SYMBOL_FUNCTION_CALL: sin [0/0] {19}
     ¦   ¦       ¦--'(': ( [0/0] {21}                       
     ¦   ¦       ¦--expr: pi [0/0] {23}                     
     ¦   ¦       ¦   °--SYMBOL: pi [0/0] {22}               
     ¦   ¦       °--')': ) [0/0] {24}                       
     ¦   °--'}': } [0/0] {25}                               
     °--'}': } [1/0] {26}                                   
