def get_strng_field(k):
    """Parse arguments of the form string:field"""
    valor = k.split(':')
    if len(valor) == 1:
        ff = []
        ss = valor[0]
    elif len(valor) == 2:
        if valor[0] == '':
            ss = '*'
        else:
            ss = valor[0]
        if valor[1] == '':
            ff = []
        else:
            ff = valor[1].split(':')
    return ss, ff
