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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 check_partitioners(partitioners, keys):
 """Checks the given partitioners. This checks that `partitioners` is a dictionary that only contains keys in `keys`, and furthermore the entries in `partitioners` are functions or further dictionaries (the latter used, for example, in passing partitioners to modules inside modules) that must satisfy the same constraints. Args: partitioners: Dictionary of partitioners (allowing nested dictionaries) or None. keys: Iterable of valid keys for `partitioners`. Returns: Checked dictionary of partitioners. If `partitioners=None`, an empty dictionary will be returned. Raises: KeyError: If an partitioner is provided for a key not in `keys`. TypeError: If a provided partitioner is not a callable function, or `partitioners` is not a Mapping. """

  if partitioners is None:
    return {}
  _assert_is_dictlike(partitioners, valid_keys=keys)

  keys = set(keys)

  if not set(partitioners) <= keys:
    extra_keys = set(partitioners) - keys
    raise KeyError(
        "Invalid partitioner keys {}, partitioners can only "
        "be provided for {}".format(
            ", ".join("'{}'".format(key) for key in extra_keys),
            ", ".join("'{}'".format(key) for key in keys)))

  _check_nested_callables(partitioners, "Partitioner")

  return partitioners