def walk_connections(self, mapping=identity):
for start in self.walk_instructions():<EOL><INDENT>for stop_instruction in start.instruction.consuming_instructions:<EOL><INDENT>if stop_instruction is None:<EOL><INDENT>continue<EOL><DEDENT>stop = self._walk.instruction_in_grid(stop_instruction)<EOL>connection = Connection(start, stop)<EOL>if connection.is_visible():<EOL><INDENT>yield mapping(connection)<EOL><DEDENT><DEDENT><DEDENT>
Iterate over connections between instructions.

        :return: an iterator over :class:`connections <Connection>` between
          :class:`instructions in grid <InstructionInGrid>`
        :param mapping: funcion to map the result, see
          :meth:`walk_instructions` for an example usage