def acquire(self, needs_lock=True):
        """Acquiring a file object from the manager.

        A new file is only opened if it has expired from the
        least-recently-used cache.

        This method uses a lock, which ensures that it is thread-safe. You can
        safely acquire a file in multiple threads at the same time, as long as
        the underlying file object is thread-safe.

        Returns
        -------
        An open file object, as returned by ``opener(*args, **kwargs)``.
        """
        with self._optional_lock(needs_lock):
            try:
                file = self._cache[self._key]
            except KeyError:
                kwargs = self._kwargs
                if self._mode is not _DEFAULT_MODE:
                    kwargs = kwargs.copy()
                    kwargs['mode'] = self._mode
                file = self._opener(*self._args, **kwargs)
                if self._mode == 'w':
                    # ensure file doesn't get overriden when opened again
                    self._mode = 'a'
                self._cache[self._key] = file
        return file