Optional transformtransform: (key, value) => {
 // Skip tokens with unknown CSS properties
 if (key.includes('unknown-css-property')) {
   return null;
 }
 // Change the value of all font-family tokens to Roboto
 if (key.includes('font-family')) {
   return { key, value: 'Roboto' };
 }
 // Return the original token
 return { key, value };
},
Optional unit
This function is called for each token. It can be used to transform the key and value of each token. If the function returns null, the token will be skipped.