inquiry regarding a3m input format

Hello, I wonder what is the correct format of a3m input for complex.

I have succeeded in using an a3m file as an input for monomer prediction,
both in the local version of ColabFold and AF2_batch notebook.
Now I want to predict a heterodimer and I have a3m files for each of them.
I tried to combine them in one file and it returns an error

2022-08-05 11:23:46,076 Could not generate input features 35_1:
setting an array element with a sequence. The requested array has an
inhomogeneous shape after 1 dimensions. The detected shape was (6,) +
inhomogeneous part.
Traceback (most recent call last):
File "/home/fbsb2/miniconda3/envs/colabfold/lib/python3.9/site-packages/colabfold/batch.py",
line 1350, in run
(input_features, domain_names) = generate_input_feature(
File "/home/fbsb2/miniconda3/envs/colabfold/lib/python3.9/site-packages/colabfold/batch.py",
line 1017, in generate_input_feature
feature_dict = build_monomer_feature(
File "/home/fbsb2/miniconda3/envs/colabfold/lib/python3.9/site-packages/colabfold/batch.py",
line 871, in build_monomer_feature
**pipeline.make_msa_features([msa]),
File "/home/fbsb2/miniconda3/envs/colabfold/lib/python3.9/site-packages/alphafold/data/pipeline.py",
line 79, in make_msa_features
features['deletion_matrix_int'] = np.array(deletion_matrix, dtype=np.int32)
ValueError: setting an array element with a sequence. The requested
array has an inhomogeneous shape after 1 dimensions. The detected
shape was (6,) + inhomogeneous part.
2022-08-05 11:23:46,077 Done

the combined a3m file looks like

name1
sequence1
hits
name2
sequence2
hits

Thank you in advance.

Start with colabfold/batch.py at generate_input_feature and build_monomer_feature, then inspect alphafold/data/pipeline.py at make_msa_features to understand the expected MSA shape. Compare those expectations with the combined a3m example; done means confirming the valid heterodimer input format or documenting the required input handling and reproducing the reported error.