写一段程序，删除字符串a中包含的字符串b，举例 输入a = “asdw”,b = “sd” 返回 字符串 “aw”，并且测试这个程序。

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<pre><code class=""language-python"" lang=""python"">def delBString(a,b):
if not isinstance(a,str):
raise TypeError(""a is not str"")
if not isinstance(b,str):
raise TypeError(""b is not str"")
if len(a) < len(b):
raise Exception('a length must large to b length')
result = []
flag = False
i=0
la = len(a)
lb = len(b)
while i <la:
j = 0
while j < lb:
if i+j < la and a[i+j] == b[j]:
j += 1
else :
j += 1
flag = False
break
flag = True
if flag:
i += lb
else:
result.append(a[i])
i += 1
return """".join(result)
</code></pre>

<pre><code class=""language-python"" lang=""python"">测试用例：
class TestdelInnerStringFunctions():
def setUp(self):
pass
def tearDown(self):
pass
def test_nomorl1(self):
assert delBString('asdqwe','we') == 'asdq'
def test_nomorl2(self):
assert delBString('asdqwe','0') == 'asdqwe'
def test_nomorl3(self):
assert delBString('测试asdqwe','we') == '测试asdq'
def test_nomorl4(self):
assert delBString('测试asdqwe','测试') == 'asdqwe'
def test_nomorl5(self):
assert delBString('asdqwe','') == 'asdqwe'
def test_nomorl6(self):
with pytest.raises(TypeError):
delBString('', 0)
def test_nomorl7(self):
with pytest.raises(TypeError):
delBString(0, 'as')
def test_nomorl8(self):
with pytest.raises(TypeError):
delBString(True)
def test_nomorl9(self):
with pytest.raises(Exception) as excinfo:
delBString('acd','acde')
assert ""a length must large to b length"" in str(excinfo.value)
assert excinfo.type == Exception
</code></pre>

<pre><code> "“`