code: private function buildDepExtensionConstraints($depItem, $depType)
      {
          if ($this->isHash($depItem)) {
              $depItem = array($depItem);
          }
  
          $result = array();
          foreach ($depItem as $subDepItem) {
              $depChannelName = 'ext';
              $depPackageName = $subDepItem['name'];
              $depVersionConstraint = $this->parse20VersionConstraint($subDepItem);
  
              $result[] = new DependencyConstraint(
                  $depType,
                  $depVersionConstraint,
                  $depChannelName,
                  $depPackageName
              );
          }
  
          return $result;
      }
docs: Builds dependency constraint of 'extension' type
  
  @param array $depItem dependency constraint or array of dependency constraints
  @param string $depType target type of building constraint.
  @return DependencyConstraint[]