code: function (arr, obj) {
                  if (!arr[obj[0]])
                      arr[obj[0]] = { normals: [], idx: [] };
                  var idx = arr[obj[0]].normals.indexOf(obj[1]);
                  return idx === -1 ? -1 : arr[obj[0]].idx[idx];
              }
docs: Search for obj in the given array.
  This function is called to check if a couple of data already exists in an array.
  
  If found, returns the index of the founded tuple index. Returns -1 if not found
  @param arr Array<{ normals: Array<number>, idx: Array<number> }>
  @param obj Array<number>
  @returns {boolean}