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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 match_file(pattern, filename):
    '''
    The function will match a pattern in a file and return
    a rex object, which will have all the matches found in the file.
    '''

    # Validate user data.

    if pattern is None:
        return None

    if os.stat(filename).st_size == 0:
        return None

    rexobj = REX(pattern, filename)

    rexpatstr = reformat_pattern(pattern)
    #print "rexpatstr: ", rexpatstr

    rexpat = re.compile(rexpatstr)
    rexobj.rex_patternstr = rexpatstr
    rexobj.rex_pattern = rexpat

    sfile = open(filename, 'r')
    data = sfile.read()
    sfile.close()

    line_count = 1
    for line in data.splitlines():
        mobj = rexpat.match(line)
        if mobj:
            populate_resobj(rexobj, mobj, line_count)

        line_count += 1

    return rexobj