YAML::PP Implementation
               ----- Syntax -----              ----- Schema -----
Load:
YAML Stream       Tokens        Event List        Data Structure
          -------->    --------->        --------->
                lex/parse                   construct
         YAML::PP::Lexer/Parser         YAML::PP::Constructor
Dump:
YAML Stream                   Event List           Data Structure
            <------------------        <---------------
                 emit                     represent
         YAML::PP::Emitter             YAML::PP::Representer