code: private function getClassString(ClassMetadata $class)
      {
          $this->visitAssociation($class->getName());
  
          $className    = $class->getName();
          $classText    = '[' . str_replace('\\', '.', $className);
          $fields       = [];
          $parent       = $this->getParent($class);
          $parentFields = $parent ? $parent->getFieldNames() : [];
  
          foreach ($class->getFieldNames() as $fieldName) {
              if (in_array($fieldName, $parentFields)) {
                  continue;
              }
  
              if ($class->isIdentifier($fieldName)) {
                  $fields[] = '+' . $fieldName;
              } else {
                  $fields[] = $fieldName;
              }
          }
  
          if (! empty($fields)) {
              $classText .= '|' . implode(';', $fields);
          }
  
          $classText .= ']';
  
          return $classText;
      }
docs: Build the string representing the single graph item
  
  @param ClassMetadata   $class
  
  @return string