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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 get(self, key, default=None):
 """Return a value for key, with a default value if it does not exist. Args: key (str):
 The key of the column to access default (object):
 The default value to use if the key does not exist. (Defaults to :data:`None`.) Returns: object: The value associated with the provided key, or a default value. Examples: When the key exists, the value associated with it is returned. 'a' The default value is :data:`None` when the key does not exist. None The default value can be overrided with the ``default`` parameter. '' '' """

        index = self._xxx_field_to_index.get(key)
        if index is None:
            return default
        return self._xxx_values[index]