laravel Eloquent relationship using Distinct

I need show data with relationship using DISTINCT.

This is my sql data :

table pochettes

id | 
49 |

table journees

id | formateurs_id | pochettes_id
1  | 3             | 49
2  | 4             | 49
3  | 3             | 49

table formateurs

id | 
3  |
4  |

model Pochette

public function Journees()
{
    return $this->hasMany('App\Journee','pochettes_id');
} 

model Journee

public function Formateurs()
{
    return $this->belongsTo('App\Formateur', 'formateurs_id');
}

I am used this code to show data with distinct formateurs because a Formateur can have many Journee in the same Pochette :

$pochette = Pochette::find(49);
foreach ($pochette->Journees->distinct('formateurs_id') as $formateur) {
            echo $formateur->formateurs_id;
            echo "<br>";
        }

But this code dosn't work, I have this error message

    **BadMethodCallException in Macroable.php line 81:
Method distinct does not exist.**

I would show this result :

3
4

not :

3
4
3