code: def _find_metric_value(session_or_group, metric_name):
    
    # Note: We can speed this up by converting the metric_values field
    # to a dictionary on initialization, to avoid a linear search here. We'll
    # need to wrap the SessionGroup and Session protos in a python object for
    # that.
    for metric_value in session_or_group.metric_values:
      if (metric_value.name.tag == metric_name.tag and
          metric_value.name.group == metric_name.group):
        return metric_value
docs: Returns the metric_value for a given metric in a session or session group.
  
    Args:
      session_or_group: A Session protobuffer or SessionGroup protobuffer.
      metric_name: A MetricName protobuffer. The metric to search for.
    Returns:
      A MetricValue protobuffer representing the value of the given metric or
      None if no such metric was found in session_or_group.