{
    "name": "gtr_sym",
    "title":"The GTR exchangability matrix",
    "result_type": "ExchangeModel[a]",
    "call": "SModel.ReversibleMarkov.gtr_sym'[sym,a]",
    "citation":"Tavare, 1986",
    "args": [
        {
            "arg_name": "sym",
            "arg_type": "List[Pair[String,Double]]",
	    "default_value":"~dirichlet_on[letter_pairs[@a],1]",
	    "description":"Symmetric exchangability matrix"
        },
        {
            "arg_name": "a",
            "arg_type": "a",
            "default_value": "getAlphabet"
        }
    ],
    "description": "Symmetric exchangability matrix from GTR",
    "extract": "all"
}
