human
Solve the following python programming problem given the following code:
def blob_to_file(filename_hint_propertyname = None, directory_hint = '') : 
    'Write the blob contents to a file, and replace them with the filename.

  Args:
    filename_hint_propertyname: If present, the filename will begin with
      the contents of this value in the entity being exported.
    directory_hint: If present, the files will be stored in this directory.

  Returns:
    A function which writes the input blob to a file.
  ' 
    directory = [] 
    def transform_function(value, bulkload_state) : 
        if (not directory) : 
            parent_dir = os.path.dirname (bulkload_state.filename) 
            directory.append (os.path.join (parent_dir, directory_hint)) 
            if (directory [0] and (not os.path.exists (directory [0]))) : 
                os.makedirs (directory [0]) 
filename_hint = 'blob_' 
        suffix = '' 
        filename = '' 
        if filename_hint_propertyname : 
            filename_hint = bulkload_state.current_entity [filename_hint_propertyname] 
            filename = os.path.join (directory [0], filename_hint) 
            if os.path.exists (filename) : 
                filename = '' 
                (filename_hint, suffix) = os.path.splitext (filename_hint) 
if (not filename) : 
            filename = tempfile.mktemp (suffix, filename_hint, directory [0]) 
f = open (filename, 'wb') 
        f.write (value) 
        f.close () 
        return filename 
return <MASK> 
    
    Given the code above, what is a proper replacement for <MASK>? Choose among: directory, directory_hint, filename_hint_propertyname
assistant
#Here is Python program to fix = '' 
.
def transform_function(