code: def eval(self):
          
          if self.and_or == 'or':
              return [Input(self.alias, file, self.cwd, 'and')
                  for file in self.files]
          return ' '.join(self.files)
docs: Evaluates the given input and returns a string containing the
          actual filenames represented. If the input token represents multiple
          independent files, then eval will return a list of all the input files
          needed, otherwise it returns the filenames in a string.