takes a dataframe's columns that would be of the form:
    ['feed003', 'failsafe_feed999', 'override_feed000', 'feed001', 'feed002']
    and returns:
    ['override_feed000', 'feed001', 'feed002', 'feed003', 'failsafe_feed999']

def sorted_feed_cols(df):
    """
    takes a dataframe's columns that would be of the form:
    ['feed003', 'failsafe_feed999', 'override_feed000', 'feed001', 'feed002']
    and returns:
    ['override_feed000', 'feed001', 'feed002', 'feed003', 'failsafe_feed999']
    """
    cols = df.columns
    ind = [int(c.split("feed")[1]) for c in cols]
    cols = zip(ind,cols)
    cols.sort()
    cols = [c[1] for c in cols]
    return cols