code: protected function write($namespace, array $data)
      {
          $file = $this->adapter->getFileName($namespace);
          $contents = $this->adapter->prepareForWriting($data);
          if (!$this->fileSystem->has($file)) {
              $this->fileSystem->write($file, $contents);
          }
  
          $this->fileSystem->update($file, $contents);
      }
docs: Write settings content of a namespace
  
  @param  string $namespace
  @param  array  $data
  @return void