docs: function printMatrix3 (m) {
    const tStr = m.elements.map(formatPrintNumber);
    const matrixString = `
    +-                         -+
    | ${tStr[0]}  ${tStr[3]}  ${tStr[6]} |
    | ${tStr[1]}  ${tStr[4]}  ${tStr[7]} |
    | ${tStr[2]}  ${tStr[5]}  ${tStr[8]} |
    +-                         -+`;
    return matrixString;
  }