code: public boolean contains(final AbstractInsnNode insn) {
          AbstractInsnNode i = first;
          while (i != null && i != insn) {
              i = i.next;
          }
          return i != null;
      }
docs: Returns <tt>true</tt> if the given instruction belongs to this list. This
  method always scans the instructions of this list until it finds the
  given instruction or reaches the end of the list.
  
  @param insn
  an instruction.
  @return <tt>true</tt> if the given instruction belongs to this list.