code: function _sanitizeCoefficients(coefficients) {
    if (coefficients == undefined) {
      coefficients = {};
    }
    for (let property in Utils.DEFAULT_ROOM_MATERIALS) {
      if (!(coefficients.hasOwnProperty(property))) {
        // If element is not present, use default coefficients.
        coefficients[property] = Utils.ROOM_MATERIAL_COEFFICIENTS[
          Utils.DEFAULT_ROOM_MATERIALS[property]];
      }
    }
    return coefficients;
  }
docs: Sanitize coefficients.
  @param {Object} coefficients
  @return {Object}