@classmethod
def get_content(cls, abspath, start=None, end=None):
    """Retrieve the content of the requested resource which is located
        at the given absolute path.

        This class method may be overridden by subclasses.  Note that its
        signature is different from other overridable class methods
        (no ``settings`` argument); this is deliberate to ensure that
        ``abspath`` is able to stand on its own as a cache key.

        This method should either return a byte string or an iterator
        of byte strings.  The latter is preferred for large files
        as it helps reduce memory fragmentation.

        .. versionadded:: 3.1
        """
    with open(abspath, 'rb') as file:
        if start is not None:
            file.seek(start)
        if end is not None:
            remaining = end - (start or 0)
        else:
            remaining = None
        while True:
            chunk_size = 64 * 1024
            if remaining is not None and remaining < chunk_size:
                chunk_size = remaining
            chunk = file.read(chunk_size)
            if chunk:
                if remaining is not None:
                    remaining -= len(chunk)
                yield chunk
            else:
                if remaining is not None:
                    assert remaining == 0
                return
