'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'

@classmethod
def get_content(cls, abspath, start=None, end=None):

    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
