def list_create(issue, list_name, element_name):
    """ Creates a list if parameters exist in issue.

    Args:
        issue(dict): an issue from GitHub.
        list_name (str): the name of the list in the issue.
        element_name (str): the field name of the element in the list.

    Returns:
        The created list or None if it does not exist.
    """
    if issue.get(list_name) is not None:
        return [element.get(element_name) for element in issue.get(list_name)]

    else:
        None