def get_campaign_variation(campaign, variation_name):
    """Returns variation from given campaign and variation_name.

    Args:
        campaign (dict): The running campaign
        variation_name (string): Variation identifier

    Returns:
        dict: Variation corresponding to variation_name in respective campaign
    """

    if not campaign or not variation_name:
        return None
    for variation in campaign.get("variations"):
        if variation.get("name") == variation_name:
            return variation
    return None