code: def parameter_constructor(cls, loader, node):
          
          value = loader.construct_scalar(node)
  
          if isinstance(value, str):
              if '=' in value:
                  (varname, varvalue) = Parser.parse_equality(value)
                  return cls(varname, varvalue)
              else:
                  return cls(value)
          else:
              return cls(value)
docs: Construct variable instance from yaml node