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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _do_batched_write_command(namespace, operation, command, docs, check_keys, opts, ctx):
 """Execute a batch of insert, update, or delete commands. """

    max_bson_size = ctx.max_bson_size
    max_write_batch_size = ctx.max_write_batch_size
    # Max BSON object size + 16k - 2 bytes for ending NUL bytes.
    # Server guarantees there is enough room: SERVER-10643.
    max_cmd_size = max_bson_size + _COMMAND_OVERHEAD

    ordered = command.get('ordered', True)

    buf = StringIO()
    # Save space for message length and request id
    buf.write(_ZERO_64)
    # responseTo, opCode
    buf.write(b"\x00\x00\x00\x00\xd4\x07\x00\x00")
    # No options
    buf.write(_ZERO_32)
    # Namespace as C string
    buf.write(b(namespace))
    buf.write(_ZERO_8)
    # Skip: 0, Limit: -1
    buf.write(_SKIPLIM)

    # Where to write command document length
    command_start = buf.tell()
    buf.write(bson.BSON.encode(command))

    # Start of payload
    buf.seek(-1, 2)
    # Work around some Jython weirdness.
    buf.truncate()
    try:
        buf.write(_OP_MAP[operation])
    except KeyError:
        raise InvalidOperation('Unknown command')

    if operation in (_UPDATE, _DELETE):
        check_keys = False

    # Where to write list document length
    list_start = buf.tell() - 4

    to_send = []

    def send_message():
        """Finalize and send the current OP_QUERY message.
        """
        # Close list and command documents
        buf.write(_ZERO_16)

        # Write document lengths and request id
        length = buf.tell()
        buf.seek(list_start)
        buf.write(struct.pack('<i', length - list_start - 1))
        buf.seek(command_start)
        buf.write(struct.pack('<i', length - command_start))
        buf.seek(4)
        request_id = _randint()
        buf.write(struct.pack('<i', request_id))
        buf.seek(0)
        buf.write(struct.pack('<i', length))
        return ctx.write_command(request_id, buf.getvalue(), to_send)

    # If there are multiple batches we'll
    # merge results in the caller.
    results = []

    idx = 0
    idx_offset = 0
    has_docs = False
    for doc in docs:
        has_docs = True
        # Encode the current operation
        key = b(str(idx))
        value = bson.BSON.encode(doc, check_keys, opts)
        # Send a batch?
        enough_data = (buf.tell() + len(key) + len(value) + 2) >= max_cmd_size
        enough_documents = (idx >= max_write_batch_size)
        if enough_data or enough_documents:
            if not idx:
                write_op = "insert" if operation == _INSERT else None
                _raise_document_too_large(
                    write_op, len(value), max_bson_size)
            result = send_message()
            results.append((idx_offset, result))
            if ordered and "writeErrors" in result:
                return results

            # Truncate back to the start of list elements
            buf.seek(list_start + 4)
            buf.truncate()
            idx_offset += idx
            idx = 0
            key = b'0'
            to_send = []
        buf.write(_BSONOBJ)
        buf.write(key)
        buf.write(_ZERO_8)
        buf.write(value)
        to_send.append(doc)
        idx += 1

    if not has_docs:
        raise InvalidOperation("cannot do an empty bulk write")

    results.append((idx_offset, send_message()))
    return results