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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 print_help_fields():
 """ Print help about fields and field formatters. """

    # Mock entries, so they fulfill the expectations towards a field definition
    def custom_manifold():
        "named rTorrent custom attribute, e.g. 'custom_completion_target'"
        return ("custom_KEY", custom_manifold)
    def kind_manifold():
        "file types that contribute at least N% to the item's total size"
        return ("kind_N", kind_manifold)

    print('')
    print("Fields are:")
    print("\n".join(["  %-21s %s" % (name, field.__doc__)
        for name, field in sorted(engine.FieldDefinition.FIELDS.items() + [
            custom_manifold(), kind_manifold(),
        ])
    ]))

    print('')
    print("Format specifiers are:")
    print("\n".join(["  %-21s %s" % (name, doc)
        for name, doc in sorted(formatting.OutputMapping.formatter_help())
    ]))
    print('')
    print("Append format specifiers using a '.' to field names in '-o' lists,\n"
          "e.g. 'size.sz' or 'completed.raw.delta'.")