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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 _pad_input(incoming):
 """Avoid IndexError and KeyError by ignoring un-related fields. Example: '{0}{autored}' becomes '{{0}}{autored}'. Positional arguments: incoming -- the input unicode value. Returns: Padded unicode value. """

    incoming_expanded = incoming.replace('{', '{{').replace('}', '}}')
    for key in _BASE_CODES:
        before, after = '{{%s}}' % key, '{%s}' % key
        if before in incoming_expanded:
            incoming_expanded = incoming_expanded.replace(before, after)
    return incoming_expanded