nit: rename local function

Author: aleclarson

packages/core/src/Controller.ts

@@ -241,16 +241,18 @@ export class Controller<State extends Indexable = UnknownProps> {
 /** Determine which keys should receive an update */
 function extractKeys(props: ControllerProps, springs: Indexable<SpringValue>) {
   const keys = new Set<AnyKey>()
-  const extract = (obj: Indexable) =>
+
+  /** Collect keys with a defined value */
+  const extractDefined = (obj: Indexable) =>
     each(obj, (value, key) => {
       if (!is.und(value)) {
         keys.add(key)
       }
     })
 
   const { from, to } = props
-  if (is.obj(to)) extract(to)
-  if (from) extract(from)
+  if (is.obj(to)) extractDefined(to)
+  if (from) extractDefined(from)
 
   // When neither "from" or "to" have a key with a defined value,
   // return the keys for every existing spring.