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<b>Warning</b>:  session_start(): open(/var/lib/php/sessions/sess_nvsndh7g6nnn915v6q3lvleo85, O_RDWR) failed: No space left on device (28) in <b>/var/www/tb-usercake/models/config.php</b> on line <b>51</b><br />
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<b>Warning</b>:  session_start(): Failed to read session data: files (path: /var/lib/php/sessions) in <b>/var/www/tb-usercake/models/config.php</b> on line <b>51</b><br />
// does not store null values
static Map indexByField(Iterable c, S field) {
  new HashMap map;
  for (O a : c) {
    O val = getOpt(a, field);
    if (val != null)
      map.put(val, a);
  }
  ret map;
}

static Map mapMethodLike indexByField(S field, Iterable c) {
  ret indexByField(c, field);
}