ReferenceError: getDimensionSize is not defined

[katopz]

export const getMeanAsRowVector = (matrix) => {
  const n = getDimensionSize(matrix, 2);
  const vectors = Array(n).fill().map((_, i) => math.eval(`matrix[:, ${i + 1}]`, { matrix }));
  return vectors.reduce((result, vector) => result.concat(math.mean(vector)), []);
};

Seem obvious here that getDimensionSize is calling from nowhere?