---input---
f"result: {value:{width}.{precision}}"

---tokens---
'f'           Literal.String.Affix
'"'           Literal.String.Double
'result: '    Literal.String.Double
'{'           Literal.String.Interpol
'value'       Name
':'           Literal.String.Interpol
'{'           Literal.String.Interpol
'width'       Name
'}'           Literal.String.Interpol
'.'           Literal.String.Double
'{'           Literal.String.Interpol
'precision'   Name
'}'           Literal.String.Interpol
'}'           Literal.String.Interpol
'"'           Literal.String.Double
'\n'          Text.Whitespace