code: def visit_BitVecShiftLeft(self, expression, *operands):
          
          left = expression.operands[0]
          right = expression.operands[1]
          if isinstance(right, BitVecConstant):
              if right.value == 0:
                  return left
              elif right.value >= right.size:
                  return left
docs: a << 0 => a                       remove zero
              a << ct => 0 if ct > sizeof(a)    remove big constant shift