<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def clear_bp(cls, ctx, register):
 """ Clears a hardware breakpoint. @see: find_slot, set_bp @type ctx: dict( str S{->} int ) @param ctx: Thread context dictionary. @type register: int @param register: Slot (debug register) for hardware breakpoint. """

        ctx['Dr7'] &= cls.clearMask[register]
        ctx['Dr%d' % register] = 0