---input---
fr'x={4*10}'

---tokens---
'fr'          Literal.String.Affix
"'"           Literal.String.Single
'x='          Literal.String.Single
'{'           Literal.String.Interpol
'4'           Literal.Number.Integer
'*'           Operator
'10'          Literal.Number.Integer
'}'           Literal.String.Interpol
"'"           Literal.String.Single
'\n'          Text.Whitespace