    %YAML 1.1   # Reference card
    ---
    Collection indicators:
        '? ' : Key indicator.
        ': ' : Value indicator.
        '- ' : Nested series entry indicator.
        ', ' : Separate in-line branch entries.
        '[]' : Surround in-line series branch.
        '{}' : Surround in-line keyed branch.
    Scalar indicators:
        '''' : Surround in-line unescaped scalar ('' escaped ').
        '"'  : Surround in-line escaped scalar (see escape codes below).
        '|'  : Block scalar indicator.
        '>'  : Folded scalar indicator.
        '-'  : Strip chomp modifier ('|-' or '>-').
        '+'  : Keep chomp modifier ('|+' or '>+').
        1-9  : Explicit indentation modifier ('|1' or '>2').
               # Modifiers can be combined ('|2-', '>+1').
    Alias indicators:
        '&'  : Anchor property.
        '*'  : Alias indicator.
    Tag property: # Usually unspecified.
        none    : Unspecified tag (automatically resolved by application).
        '!'     : Non-specific tag (by default, "!!map"/"!!seq"/"!!str").
        '!foo'  : Primary (by convention, means a local "!foo" tag).
        '!!foo' : Secondary (by convention, means "tag:yaml.org,2002:foo").
        '!h!foo': Requires "%TAG !h! <prefix>" (and then means "<prefix>foo").
        '!<foo>': Verbatim tag (always means "foo").
    Document indicators:
        '%'  : Directive indicator.
        '---': Document header.
        '...': Document terminator.
    Misc indicators:
        ' #' : Throwaway comment indicator.
        '`@' : Both reserved for future use.
    Special keys:
        '='  : Default "value" mapping key.
        '<<' : Merge keys from another mapping.
    Core types: # Default automatic tags.
        '!!map' : { Hash table, dictionary, mapping }
        '!!seq' : { List, array, tuple, vector, sequence }
        '!!str' : Unicode string
    More types:
        '!!set' : { cherries, plums, apples }
        '!!omap': [ one: 1, two: 2 ]
    Language Independent Scalar types:
        { ~, null }              : Null (no value).
        [ 1234, 0x4D2, 02333 ]   : [ Decimal int, Hexadecimal int, Octal int ]
        [ 1_230.15, 12.3015e+02 ]: [ Fixed float, Exponential float ]
        [ .inf, -.Inf, .NAN ]    : [ Infinity (float), Negative, Not a number ]
        { Y, true, Yes, ON  }    : Boolean true
        { n, FALSE, No, off }    : Boolean false
        ? !!binary >
            R0lG...BADS=
        : >-
            Base 64 binary value.
    Escape codes:
     Numeric   : { "\x12": 8-bit, "\u1234": 16-bit, "\U00102030": 32-bit }
     Protective: { "\\": '\', "\"": '"', "\ ": ' ', "\<TAB>": TAB }
     C         : { "\0": NUL, "\a": BEL, "\b": BS, "\f": FF, "\n": LF, "\r": CR,
                   "\t": TAB, "\v": VTAB }
     Additional: { "\e": ESC, "\_": NBSP, "\N": NEL, "\L": LS, "\P": PS }
    ...

From http://www.yaml.org/refcard.html.
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