code: def get_families(data_dir=None):
      '''Return a list of all basis set families'''
      data_dir = fix_data_dir(data_dir)
      metadata = get_metadata(data_dir)
  
      families = set()
      for v in metadata.values():
          families.add(v['family'])
  
      return sorted(list(families)f get_families(data_dir=None):
      '''Return a list of all basis set families'''
      data_dir = fix_data_dir(data_dir)
      metadata = get_metadata(data_dir)
  
      families = set()
      for v in metadata.values():
          families.add(v['family'])
  
      return sorted(list(families))
docs: Return a list of all basis set families