def get_func_description_from_docstring(docstring):
    """
    Get the string of the function's description in docstring.

    Parameters
    ----------
    docstring : str
        Target docstring.

    Returns
    ----------
    func_description : str
        Description of the function in docstring.
    """
    if docstring == '':
        return ''
    last_line_num = 0
    line_splitted_list = docstring.split('\n')
    for line_str in line_splitted_list:
        is_hyphen_line = '----' in line_str
        if is_hyphen_line:
            last_line_num -= 1
            break
        last_line_num += 1
    if last_line_num <= 0:
        return ''
    func_description = '\n'.join(line_splitted_list[:last_line_num])
    func_description = func_description.strip()
    if func_description.replace(' ', '') == '':
        return ''
    if not func_description.startswith('    '):
        func_description = '    %s' % func_description
    return func_description
