[
    [ BeginEnv "signature"
    , Label "example_pair"
    , BeginEnv "math"
    , ParenL
    , Variable "x"
    , Symbol ","
    , Variable "y"
    , ParenR
    , EndEnv "math"
    , Word "is"
    , Word "a"
    , Word "set"
    , Symbol "."
    , EndEnv "signature"
    ]
,
    [ BeginEnv "proposition"
    , Label "mathrel_notation_test"
    , Word "if"
    , BeginEnv "math"
    , Variable "x"
    , Command "mathrel"
    , InvisibleBraceL
    , Variable "R"
    , InvisibleBraceR
    , Variable "y"
    , EndEnv "math"
    , Symbol ","
    , Word "then"
    , BeginEnv "math"
    , Variable "x"
    , Command "mathrel"
    , InvisibleBraceL
    , Variable "R"
    , InvisibleBraceR
    , Variable "y"
    , EndEnv "math"
    , Symbol "."
    , EndEnv "proposition"
    ]
]