function pickBy( obj, predicate ) {
	var keys;
	var out;
	var key;
	var i;
	if ( typeof obj !== 'object' || obj === null ) {
		throw new TypeError( format( 'invalid argument. First argument must be an object. Value: `%s`.', obj ) );
	}
	if ( !isFunction( predicate ) ) {
		throw new TypeError( format( 'invalid argument. Second argument must be a function. Value: `%s`.', predicate ) );
	}
	out = {};
	keys = objectKeys( obj );
	for ( i = 0; i < keys.length; i++ ) {
		key = keys[ i ];
		if ( predicate( key, obj[ key ] ) ) {
			out[ key ] = obj[ key ];
		}
	}
	return out;
}
Returns a partial object copy containing properties for which a predicate returns a truthy value.

@param {Object} obj - source object
@param {Function} predicate - predicate function
@throws {TypeError} first argument must be an object
@throws {TypeError} second argument must be a function
@returns {Object} new object

@example
function predicate( key, value ) {
    return ( value > 1 );
}

var obj1 = {
    'a': 1,
    'b': 2
};

var obj2 = pickBy( obj1, predicate );
// returns { 'b': 2 }