<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def read_requirements(req_file):
 """Reads a requirements file. Args: req_file (str):
 Filename of requirements file """

    items = list(parse_requirements(req_file, session={}))
    result = []

    for item in items:
        # Get line number from item
        line_number = item.comes_from.split(req_file + ' (line ')[1][:-1]
        if item.req:
            item.req.marker = item.markers
            result.append((item.req, line_number))
        else:
            result.append((item, line_number))

    return result