def check_source_place_presence(net):
    """
    Check if there is a unique source place with empty connections

    Parameters
    -------------
    net
        Petri net

    Returns
    -------------
    place
        Unique source place (or None otherwise)
    """
    count_empty_input = 0
    unique_source = None
    for place in net.places:
        if len(place.in_arcs) == 0:
            count_empty_input = count_empty_input + 1
            unique_source = place
    if count_empty_input == 1:
        return unique_source
    return None