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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def decode(self, bytes, raw=False, index=None):
 """Decodes the given bytes according to this Field Definition. If raw is True, no enumeration substitutions will be applied to the data returned. If index is an integer or slice (and the type of this FieldDefinition is an ArrayType), then only the element(s) at the specified position(s) will be decoded. """

        if index is not None and isinstance(self.type, dtype.ArrayType):
            value = self.type.decode( bytes[self.slice()], index, raw )
        else:
            value = self.type.decode( bytes[self.slice()], raw )


        # Apply bit mask if needed
        if self.mask is not None:
            value &= self.mask

        if self.shift > 0:
            value >>= self.shift

        if not raw and self.enum is not None:
            value = self.enum.get(value, value)

        return value