def parse_einsum_interleaved(operand_sublists):
    """
    Parse einsum expression in interleaved format, retaining ellipses if present.

    Return operands as well as output mode labels if explicit form or None for implicit form.
    """
    inputs   = list()
    operands = list()

    N = len(operand_sublists) // 2
    for i in range(N):
        operands.append(operand_sublists[2*i])
        inputs.append(operand_sublists[2*i + 1])

    N = len(operand_sublists)
    output = operand_sublists[N-1] if N % 2 == 1 else None

    return operands, inputs, output