{
    "name": "x3_sym",
    "constraints": [ "Triplets[a,b]" ],
    "result_type": "ExchangeModel[a]",
    "title": "Exchangability matrix on triplets/codon constructed from nucleotide exchange rates",
    "call": "SModel.Codons.x3_sym[a,submodel]",
    "args": [
        {
            "arg_name": "submodel",
            "arg_type": "ExchangeModel[b]",
            "alphabet": "getNucleotides[@a]",
	    "description": "The singlet exchange model"
        },
        {
            "arg_name": "a",
            "arg_type": "a",
            "default_value": "getAlphabet",
	    "description": "The Triplets alphabet"
        }
    ],
    "description": "Exchangability matrix on triplets or codons constructed from an exchangability matrix on nucleotides.\n\nThus function can be used to build up triplet and codon models incrementally.",
    "examples": ["hky85_sym+x3_sym+f+dNdS      // equivalent to gy94","gtr_sym+x3_sym+f","x3_sym[hky85_sym]"],
    "see": ["gy94","gy94_ext"]
}
