function enum2str( operation ) {
	var v = hash[ operation ];
	return ( typeof v === 'string' ) ? v : null; // note: we include this guard to prevent walking the prototype chain
}
Returns the BLAS operation side string associated with a BLAS operation side enumeration constant.

@param {integer} operation - operation enumeration constant
@returns {(string|null)} operation string or null

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

var v = str2enum( 'left' );
// returns <number>

var s = enum2str( v );
// returns 'left'