import mimetypes


def get_content_type(filename):
    """
    Uses mimetype's guess functionality to take a shot at guessing the provided filename's mimetype.

    :param str filename: name of the file, should include extension
    :return: the guessed value or `application/octet-stream` by default
    :rtype: str
    """
    return mimetypes.guess_type(filename)[0] or 'application/octet-stream'