def add_step(self, setting, duration):
if len(self._prog_steps) < <NUM_LIT:10>:<EOL><INDENT>self._prog_steps.append(ProgramStep(self, setting, duration))<EOL><DEDENT>else:<EOL><INDENT>raise IndexError("<STR_LIT>")<EOL><DEDENT>
Adds steps to a program.
:param setting: Current, Wattage or Resistance, depending on program mode.
:param duration: Length of step in seconds.
:return: None