Adding all files from given path to the object.

        Args:
            path (str): valid, existing directory

def add_path(self, path, path_filter=None):
        """
        Adding all files from given path to the object.

        Args:
            path (str): valid, existing directory
        """
        for root, _, files in os.walk(path):
            for filename in files:
                full_path_and_filename = os.path.join(root, filename)
                if path_filter is None or path_filter(full_path_and_filename):
                    relative_path_and_filename = full_path_and_filename.replace(path + '/', '')
                    with open(full_path_and_filename, 'rb') as handle:
                        self.files[relative_path_and_filename] = b64encode(handle.read()).decode('utf-8')