Really odd function - used to help ensure we actually warn for duplicate
        keys.

def _warn_dupkey(self, k):
        """
        Really odd function - used to help ensure we actually warn for duplicate
        keys.
        """
        if self._privflags & PYCBC_CONN_F_WARNEXPLICIT:
            warnings.warn_explicit(
                'Found duplicate keys! {0}'.format(k), RuntimeWarning,
                __file__, -1, module='couchbase_ffi.bucket', registry={})
        else:
            warnings.warn('Found duplicate keys!', RuntimeWarning)