<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def normalize_input_value(value):
 """ Returns an input value normalized for RightScale API 2.0. This typically means adjusting the *input type* prefix to be one of the valid values:: blank ignore inherit text: env: cred: key: array: This list comes from the table published here: http://reference.rightscale.com/api1.5/resources/ResourceInputs.html#multi_update If unspecified, value is assumed to be a of type ``text``. """

    if value in ('blank', 'ignore', 'inherit'):
        return value

    # assume any unspecified or unknown types are text
    tokens = value.split(':')
    if (len(tokens) < 2
            or tokens[0] not in ('text', 'env', 'cred', 'key', 'array')):
        return 'text:%s' % value

    return value