Returns ctype arrays for keys and values(converted to strings) in a dictionary

def _ctype_dict(param_dict):
    """
    Returns ctype arrays for keys and values(converted to strings) in a dictionary
    """
    assert(isinstance(param_dict, dict)), \
        "unexpected type for param_dict: " + str(type(param_dict))
    c_keys = c_array(ctypes.c_char_p, [c_str(k) for k in param_dict.keys()])
    c_vals = c_array(ctypes.c_char_p, [c_str(str(v)) for v in param_dict.values()])
    return (c_keys, c_vals)