'Get the size of the instruction specified by `insn_addr`.
:param int insn_addr: Address of the instruction
:return: Size of the instruction in bytes, or None if the instruction is not found.
:rtype: int'

def instruction_size(self, insn_addr):

    for b in self.blocks:
        block = self._get_block(b.addr, size=b.size)
        if (insn_addr in block.instruction_addrs):
            index = block.instruction_addrs.index(insn_addr)
            if (index == (len(block.instruction_addrs) - 1)):
                size = ((block.addr + block.size) - insn_addr)
            else:
                size = (block.instruction_addrs[(index + 1)] - insn_addr)
            return size
    return None
