#!/usr/bin/env python
# -*- coding: UTF-8 -*-

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#   http://www.apache.org/licenses/LICENSE-2.0
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# Copied from trac/utils.py, ticket-links-trunk branch
def unique(seq):
    """Yield unique elements from sequence of hashables, preserving order.
    (New in 0.13)
    """
    seen = set()
    return (x for x in seq if x not in seen and not seen.add(x))