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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 validate_field_name(bases: List[Type['BaseModel']], field_name: str) -> None: """ Ensure that the field's name does not shadow an existing attribute of the model. """

    for base in bases:
        if getattr(base, field_name, None):
            raise NameError(
                f'Field name "{field_name}" shadows a BaseModel attribute; '
                f'use a different field name with "alias=\'{field_name}\'".'
            )