def METHOD_NAME(self, input_files, text_to_append='dipy', out_dir='',
        out_file='append.txt'):
    """
    Parameters
    ----------
    input_files : string
        Path to the input files. This path may contain wildcards to
        process multiple inputs at once.
    text_to_append : string, optional
        Text that will be appended to the file. (default 'dipy')
    out_dir : string, optional
        Where the resulting file will be saved. (default '')
    out_file : string, optional
        Name of the result file to be saved. (default 'append.txt')
    """
    """
    ``AppendTextFlow`` is the name of our workflow. Note that it needs
    to extend Workflow for everything to work properly. It will append
    text to a file.
    It is mandatory to have out_dir as a parameter. It is also mandatory
    to put `out_` in front of every parameter that is going to be an
    output. Lastly, all `out_` params needs to be at the end of the params
    list.
    The ``run`` docstring is very important, you need to document every
    parameter as they will be used with inspection to build the command line
    argument parser.
    """
    io_it = self.get_io_iterator()
    for in_file, out_file in io_it:
        shutil.copy(in_file, out_file)
        with open(out_file, 'a') as myfile:
            myfile.write(text_to_append)