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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 parse_colname(colname):
 """ Common function to interpret input column names provided by the user. This function translates column specification provided by the user into a column number. Notes ----- This function will understand the following inputs:: '1,2,3' or 'c1,c2,c3' or ['c1','c2','c3'] '1-3' or 'c1-c3' '1:3' or 'c1:c3' '1 2 3' or 'c1 c2 c3' '1' or 'c1' 1 Parameters colname : Column name or names to be interpreted Returns ------- cols : list The return value will be a list of strings. """

    if isinstance(colname, list):
        cname = ''
        for c in colname:
            cname += str(c) + ','
        cname = cname.rstrip(',')
    elif isinstance(colname, int) or colname.isdigit():
        cname = str(colname)
    else:
        cname = colname

    if 'c' in cname[0]:
        cname = cname.replace('c', '')

    ctok = None
    cols = None
    if '-' in cname:
        ctok = '-'
    if ':' in cname:
        ctok = ':'
    if ctok is not None:
        cnums = cname.split(ctok)
        c = list(range(int(cnums[0]), int(cnums[1]) + 1))
        cols = [str(i) for i in c]

    if cols is None:
        ctok = ',' if ',' in cname else ' '
        cols = cname.split(ctok)

    return cols