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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def currentdir(self) -> str: """Name of the current working directory containing the relevant files. To show most of the functionality of |property| |FileManager.currentdir| (unpacking zip files on the fly is explained in the documentation on function (|FileManager.zip_currentdir|), we first prepare a |FileManager| object corresponding to the |FileManager.basepath| `projectname/basename`: At first, the base directory is empty and asking for the current working directory results in the following error: Traceback (most recent call last):
 RuntimeError: The current working directory of the FileManager object \ has not been defined manually and cannot be determined automatically: \ If only one directory exists, it is considered as the current working directory automatically: 'dir1' |property| |FileManager.currentdir| memorises the name of the current working directory, even if another directory is later added to the base path: 'dir1' Set the value of |FileManager.currentdir| to |None| to let it forget the memorised directory. After that, asking for the current working directory now results in another error, as it is not clear which directory to select: Traceback (most recent call last):
 RuntimeError: The current working directory of the FileManager object \ has not been defined manually and cannot be determined automatically: \ (dir1 and dir2). Setting |FileManager.currentdir| manually solves the problem: 'dir1' Remove the current working directory `dir1` with the `del` statement: False |FileManager| subclasses can define a default directory name. When many directories exist and none is selected manually, the default directory is selected automatically. The following example shows an error message due to multiple directories without any having the default name: Traceback (most recent call last):
 RuntimeError: The current working directory of the FileManager object \ has not been defined manually and cannot be determined automatically: The \ default directory (dir3) is not among the available directories (dir1 and dir2). We can fix this by adding the required default directory manually: 'dir3' Setting the |FileManager.currentdir| to `dir4` not only overwrites the default name, but also creates the required folder: 'dir4' ['dir1', 'dir2', 'dir3', 'dir4'] Failed attempts in removing directories result in error messages like the following one: Traceback (most recent call last):
 AttributeError: While trying to delete the current working directory \ Then, the current working directory still exists and is remembered by |FileManager.currentdir|: 'dir4' ['dir1', 'dir2', 'dir3', 'dir4'] """

        if self._currentdir is None:
            directories = self.availabledirs.folders
            if len(directories) == 1:
                self.currentdir = directories[0]
            elif self.DEFAULTDIR in directories:
                self.currentdir = self.DEFAULTDIR
            else:
                prefix = (f'The current working directory of the '
                          f'{objecttools.classname(self)} object '
                          f'has not been defined manually and cannot '
                          f'be determined automatically:')
                if not directories:
                    raise RuntimeError(
                        f'{prefix} `{objecttools.repr_(self.basepath)}` '
                        f'does not contain any available directories.')
                if self.DEFAULTDIR is None:
                    raise RuntimeError(
                        f'{prefix} `{objecttools.repr_(self.basepath)}` '
                        f'does contain multiple available directories '
                        f'({objecttools.enumeration(directories)}).')
                raise RuntimeError(
                    f'{prefix} The default directory ({self.DEFAULTDIR}) '
                    f'is not among the available directories '
                    f'({objecttools.enumeration(directories)}).')
        return self._currentdir