code: def get_data_dir(module_name: str) -> str:
      
      module_name = module_name.lower()
      data_dir = os.path.join(BIO2BEL_DIR, module_name)
      os.makedirs(data_dir, exist_ok=True)
      return data_dir
docs: Ensure the appropriate Bio2BEL data directory exists for the given module, then returns the file path.
  
      :param module_name: The name of the module. Ex: 'chembl'
      :return: The module's data directory