---input---
sum by (app, proc) (instance_memory_usage_bytes)

---tokens---
'sum'         Keyword
' '           Text.Whitespace
'by'          Keyword
' '           Text.Whitespace
'('           Operator
'app'         Name.Variable
','           Punctuation
' '           Text.Whitespace
'proc'        Name.Variable
')'           Operator
' '           Text.Whitespace
'('           Operator
'instance_memory_usage_bytes' Name.Variable
')'           Operator
'\n'          Text.Whitespace