Loads resources from the specified file into the given collection
    resource.

    If no content type is provided, an attempt is made to look up the
    extension of the given filename in the MIME content type registry.

def load_into_collection_from_file(collection, filename,
                                   content_type=None):
    """
    Loads resources from the specified file into the given collection
    resource.

    If no content type is provided, an attempt is made to look up the
    extension of the given filename in the MIME content type registry.
    """
    if content_type is None:
        ext = os.path.splitext(filename)[1]
        try:
            content_type = MimeTypeRegistry.get_type_for_extension(ext)
        except KeyError:
            raise ValueError('Could not infer MIME type for file extension '
                             '"%s".' % ext)
    load_into_collection_from_stream(collection, open(filename, 'rU'),
                                     content_type)