How do I write this python code to prevent duplicate integers from being inserted into the array?

class BufferArray: def __init__(self): self._numberofelements = 0 self._buffer_size = 20 # None is used to define a null data type or no value at all. self._intArray = [None] * self._buffer_size def insert(self, value): if self._numberofelements == self._buffer_size - 1: return False else: self._intArray[self._numberofelements] = value self._numberofelements += 1 return True # def display(self): print(",".join(map(str, self._intArray[:self._numberofelements]))) # def locationOf(self, value): if value in self._intArray: print(self._intArray.index(value)) else: print(-1) # def find(self, value): if value in self._intArray: print(True) else: print(False) # def fastRemove(self, value): if value in self._intArray.index(value): index = self._intArray.index(value) self._intArray[index], self._intArray[self._numberofelements - 1] = self._intArray[self._numberofelements - 1], \self._intArray[index] self._numberofelements -= 1 return True else: return False # def stableRemove(self, value): if value in self._intArray: index = self._intArray.index(value) self._intArray = self._intArray[:index] + self._intArray[index + 1:] self._numberofelements -= 1 return True else: return False # children classes class ArrayBufferNoDups(BufferArray): def __init__(self): super().__init__() self._numberofelements = 0 self._buffer_size = 20 # None is used to define a null data type or no value at all. self._intArray = [None] * self._buffer_size

def insert(self, value): if self._numberofelements == self._buffer_size - 1: return False elif value in self._intArray.index(value): return False else: self._intArray[self._numberofelements] = value self._numberofelements += 1 return True