Unresolved reference warning when iterating over 'input' key-value pairs using '.items()'

[BertBog]

Hey,

I have encountered this minor issue where .items() is not recognized for the Snakemake input.
For example:

rule a:
    input:
        IN_A = 'file_a.txt',
        IN_B = 'file_b.txt',
    output:
        OUT = 'all.txt'
    run:
        with open(output.OUT, 'w') as handle:
            for key, path in input.items():
                handle.write(path)

In this case PyCharm gives the warning: unresolved reference 'items' in 'input'