import io


class UploadedFile:
    def __init__(self, filename: str = None):
        self.filename = filename
        self.body_b64 = io.BytesIO()


def from_bytes(input_bytes: bytes) -> UploadedFile:
    """
    Builds the UploadedFile from its serialized (byte array) form.
    :param input_bytes: serialized message
    :return: UploadedFile instance
    """
    prolog_len = (input_bytes[0] << 8) + input_bytes[1]
    metadata = input_bytes[2:prolog_len + 2].decode()
    body_b64 = input_bytes[prolog_len + 2:]

    return UploadedFile()