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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 _handle_key_value(t_dict, key, value):
 """ Function to handle key has multi value, and return the values as list. """

    if key in t_dict:
        val = t_dict[key]
        if isinstance(val, str):
            val = [val]
        val.append(value)
        return val
    return value