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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 injectables_specs_for_key(self, key):
 """Given a key, yield all relevant injectable spec addresses. :API: public """

    mapping = self.injectables_spec_mapping
    if key not in mapping:
      raise self.NoMappingForKey(key)
    specs = mapping[key]
    assert isinstance(specs, list), (
      'invalid `injectables_spec_mapping` on {!r} for key "{}". '
      'expected a `list` but instead found a `{}`: {}'
    ).format(self, key, type(specs), specs)
    return [Address.parse(s).spec for s in specs]