code: def filenames(self) -> List[str]:
          
          return sorted(
              fn for fn in os.listdir(self.currentpath)
              if not fn.startswith('_'))
docs: Names of the files contained in the the current working directory.
  
          Files names starting with underscores are ignored:
  
          >>> from hydpy.core.filetools import FileManager
          >>> filemanager = FileManager()
          >>> filemanager.BASEDIR = 'basename'
          >>> filemanager.projectdir = 'projectname'
          >>> from hydpy import TestIO
          >>> with TestIO():
          ...     filemanager.currentdir = 'testdir'
          ...     open('projectname/basename/testdir/file1.txt', 'w').close()
          ...     open('projectname/basename/testdir/file2.npy', 'w').close()
          ...     open('projectname/basename/testdir/_file1.nc', 'w').close()
          ...     filemanager.filenames
          ['file1.txt', 'file2.npy']