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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 to_feather(df, path):
 """ Write a DataFrame to the feather-format Parameters df : DataFrame path : string file path, or file-like object """

    path = _stringify_path(path)
    if not isinstance(df, DataFrame):
        raise ValueError("feather only support IO with DataFrames")

    feather = _try_import()[0]
    valid_types = {'string', 'unicode'}

    # validate index
    # --------------

    # validate that we have only a default index
    # raise on anything else as we don't serialize the index

    if not isinstance(df.index, Int64Index):
        raise ValueError("feather does not support serializing {} "
                         "for the index; you can .reset_index()"
                         "to make the index into column(s)".format(
                             type(df.index)))

    if not df.index.equals(RangeIndex.from_range(range(len(df)))):
        raise ValueError("feather does not support serializing a "
                         "non-default index for the index; you "
                         "can .reset_index() to make the index "
                         "into column(s)")

    if df.index.name is not None:
        raise ValueError("feather does not serialize index meta-data on a "
                         "default index")

    # validate columns
    # ----------------

    # must have value column names (strings only)
    if df.columns.inferred_type not in valid_types:
        raise ValueError("feather must have string column names")

    feather.write_feather(df, path)