It appears that the repository has undergone several changes and renamings:

backend/node_modules/postcss-value-parser/lib/walk.js

@@ -1,22 +0,0 @@
-module.exports = function walk(nodes, cb, bubble) {
-  var i, max, node, result;
-
-  for (i = 0, max = nodes.length; i < max; i += 1) {
-    node = nodes[i];
-    if (!bubble) {
-      result = cb(node, i, nodes);
-    }
-
-    if (
-      result !== false &&
-      node.type === "function" &&
-      Array.isArray(node.nodes)
-    ) {
-      walk(node.nodes, cb, bubble);
-    }
-
-    if (bubble) {
-      cb(node, i, nodes);
-    }
-  }
-};