function resolve( operation ) {
	var t = ( typeof operation );
	if ( t === 'string' ) {
		return ( str2enum( operation ) === null ) ? null : operation;
	}
	if ( t === 'number' ) {
		return enum2str( operation );
	}
	return null;
}
Returns the operation side string associated with a supported BLAS operation side value.

@param {*} operation - operation value
@returns {(string|null)} operation side string or null

@example
var str2enum = require( '@stdlib/blas/base/operation-side-str2enum' );

var v = resolve( str2enum( 'left' ) );
// returns 'left'