export type BaseType =
  | 'length'
  | 'angle'
  | 'time'
  | 'frequency'
  | 'resolution'
  | 'flex'
  | 'percentage';
/**
 * @param {string} unit
 * @return {BaseType | null}
 */
export function baseOf(unit: string): BaseType | null;
/**
 * Convert a value within a single conversion family. Returns null when
 * either unit is missing from the table (em/rem/vw need runtime context)
 * or when the units belong to different base types.
 * @param {number} value
 * @param {string} from
 * @param {string} to
 * @return {number | null}
 */
export function convert(value: number, from: string, to: string): number | null;