Laravel 5.8 Call to undefined relationship [sourceClient] on model

I have a model WorkflowStep with a Polyphormic relation to TransportWorkflowStep and TransformworkflowStep

My transportWorkflowStep has an other relation to client.

When I do this in my code:

/** @var TransportWorkflowStep $workflowStepEntity */
$workflowStepEntity = $workflowStep->entity;

try {
    var_dump($workflowStepEntity->sourceClient);
} catch (\Exception $exception) {
    dd($exception);
}

I get this error:

Call to undefined relationship [sourceClient] on model [App\TransformWorkflowStep].

First weird thing is that I am working with TransportWorkflowStep when I dd($workflowstep) so I don’t know why he’s complaining about TransformWorkflowStep

My WorkflowStep model:

public function entity(): MorphTo
{
    return $this->morphTo();
}

My TransportWorkflowStep model:

public function workflowStep(): MorphOne
{
    return $this->morphOne(WorkflowStep::class, 'entity');
}

public function sourceClient(): BelongsTo
{
    return $this->belongsTo(Client::class, 'source_id', 'id');
}

public function destinationClient(): BelongsTo
{
    return $this->belongsTo(Client::class, 'destination_id', 'id');
}

My TransformWorkflowStep model:

public function workflowStep(): MorphOne
{
    return $this->morphOne(WorkflowStep::class, 'entity');
}

via Chebli Mohamed