code: public function getValue($key)
      {
          $allKeys = $this->getKeys([$key]);
          if (array_key_exists($key, $allKeys)) {
              return $allKeys[$key]['value'];
          }
          throw new KeyNotFoundException('Requested key not found in your file.');
      }
docs: Return the value matching to a given key in the file content
  
  @param  $key
  
  @throws \Jackiedo\DotenvEditor\Exceptions\KeyNotFoundException
  
  @return string