def list_contexts(flowlist):
    """Displays list of contexts along with 1 if the context is present for that flowclass.
    Can send a preferred list or
        :param flowlist: A FlowList in standard format
    :return: pandas df with 'Context',plus columns for all flow classes
    """
    contexts = flowlist[['Context', 'Class']]
    contexts = contexts.drop_duplicates()
    contexts['Num'] = 1
    context_counts = contexts.pivot_table(index='Context', columns='Class',
                                          values='Num', aggfunc='count',
                                          fill_value='0').reset_index()
    return context_counts