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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 read_nb_content(cells, mod_name):
    "Build a dictionary containing the position of the `cells`."
    doc_fns = {}
    for i, cell in enumerate(cells):
        if cell['cell_type'] == 'code':
            for match in SHOW_DOC_RE.findall(cell['source']):
                doc_fns[match] = i
    return doc_fns