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

@param {integer} value - diagonal type enumeration constant
@returns {(string|null)} diagonal type string or null

@example
var str2enum = require( '@stdlib/blas/base/diagonal-type-str2enum' );

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

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