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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 mk_field(field):
 """Instantiates a field specification from a parsed "AST" of a field. Parameters field : dict Returns A Field or a specialization of a field, like a bitfield. """

  assert len(field) == 1
  identifier, contents = next(iter(field.items()))
  contents = dict(list({'units': '', 'n_with_values': 0}.items()) + list(contents.items()))
  return sbp.resolve_type(sbp.Field(identifier=identifier,
                                    type_id=contents.pop('type'),
                                    options=contents))