function alias2related( alias ) {
	if ( !isString( alias ) ) {
		throw new TypeError( format( 'invalid argument. Must provide a string. Value: `%s`.', alias ) );
	}
	if ( hasOwnProp( ALIAS_TO_RELATED, alias ) ) {
		return ALIAS_TO_RELATED[ alias ].slice();
	}
	return null;
}
Returns aliases related to a specified alias.

@param {string} alias - alias
@throws {TypeError} must provide a string
@returns {(Array|StringArray|null)} related aliases

@example
var v = alias2related( 'base.sin' );
// returns [...]