code: def build_tree_fast(self, new_path=None, seq_type='nucl' or 'prot'):
          
          # Check output #
          if new_path is None: new_path = self.prefix_path + '.tree'
          # Command #
          command_args = []
          if seq_type == 'nucl': command_args += ['-nt']
          command_args += ['-gamma']
          command_args += ['-out', new_path]
          command_args += [self.path]
          # Run it #
          sh.FastTree(*command_args)
          # Return #
          return FilePath(new_path)
docs: Make a tree with FastTree. Names will be truncated however.