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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 __x_google_quota_definitions_descriptor(self, limit_definitions):
 """Describes the quota limit definitions for an API. Args: limit_definitions: List of endpoints.LimitDefinition tuples Returns: A dict descriptor of the API's quota limit definitions. """

    if not limit_definitions:
      return None

    definitions_list = [{
        'name': ld.metric_name,
        'metric': ld.metric_name,
        'unit': '1/min/{project}',
        'values': {'STANDARD': ld.default_limit},
        'displayName': ld.display_name,
    } for ld in limit_definitions]

    metrics = [{
        'name': ld.metric_name,
        'valueType': 'INT64',
        'metricKind': 'GAUGE',
    } for ld in limit_definitions]

    return {
        'quota': {'limits': definitions_list},
        'metrics': metrics,
    }