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

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