'Calculate the total size of leading nop instructions.
:param insns: A list of capstone insn objects.
:return: Number of bytes of leading nop instructions.
:rtype: int'

@classmethod
def _get_nop_length(cls, insns):

    nop_length = 0
    if (insns and cls._is_noop_insn(insns[0])):
        for insn in insns:
            if cls._is_noop_insn(insn):
                nop_length += insn.size
            else:
                break
    return nop_length
