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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 dashes_to_unders_in_keys(self) -> None: """Replaces dashes with underscores in key names. For each attribute in a mapping, this replaces any dashes in \ its keys with underscores. Handy because Python does not \ accept dashes in identifiers, while some YAML-based file \ formats use dashes in their keys. """

        for key_node, _ in self.yaml_node.value:
            key_node.value = key_node.value.replace('-', '_')