@abstractmethod<EOL><INDENT>def map(self, context):<DEDENT>
pass<EOL>
Called once for each key/value pair in the input
split. Applications must override this, emitting an output
key/value pair through the context.

:type context: :class:`Context`
:param context: the context object passed by the
  framework, used to get the input key/value pair and emit the
  output key/value pair.