FieldItemBase::setValue

public FieldItemBase::setValue($values, $notify = TRUE)

public function setValue($values, $notify = TRUE) {
  // Treat the values as property value of the first property, if no array is
  // given.
  if (isset($values) && !is_array($values)) {
    $keys = array_keys($this->definition->getPropertyDefinitions());
    $values = array($keys[0] => $values);
  }
  parent::setValue($values, $notify);
}