code: def extension(driver):
      """Returns file extension of driver
  
      Parameters
      ----------
      driver : str
  
      Returns
      -------
      str
          File extensions or None if not specified by driver
  
      """
  
      return _get_metadata_item(driver, MetadataItem.EXTENSION)
  
file_path: Fiona/fiona/meta.py
imports: import logging
  import xml.etree.ElementTree
  from fiona.env import require_gdal_version
  from fiona.ogrext import _get_metadata_item
label_desc: Use image node_id 7 for calling a global function with example usage: extension(driver) and returns: _get_metadata_item