Accept a dict of key:values (numerics) returning list of key-value tuples ordered by desc values.

    If by_key=True, sorts by dict key.

def sort_dict(key_counts, by_key=False):
    '''Accept a dict of key:values (numerics) returning list of key-value tuples ordered by desc values.

    If by_key=True, sorts by dict key.'''
    sort_key = lambda x: (-1 * x[1], x[0])
    if by_key:
        sort_key = lambda x: x[0]
    return sorted(key_counts.items(), key=sort_key)