title: Importing time series with json_normalize from opentsdb
body: <p>Trying to import data from OpenTSDB using json_normalize. Somehow it worked for most field except the values of each timestamp. </p>
  
  <p>I've tried to change different settings and even the <code>.T</code> at the end for time series which I got somewhere around here. Although, that did not help.</p>
  
  <pre><code>import pandas as pd
  from pandas.io.json import json_normalize
  
  data = {
      "metric": "peer.traffic.in",
      "tags": {"site": "site1", "peer": "peer1"},
      "aggregateTags": [],
      "dps": {"1561953835": 19565.66015625, "1561954125": 19012.55078125, "1561954439": 17274.669921875, "1561954728": 19151.75, "1561955039": 17603.23046875, "1561955329": 17056.1796875, "1561955641": 16232.349609375, "1561955928": 17016.48046875, "1561956241": 16023.0498046875, "1561956533": 15529.1298828125, "1561956847": 14976.080078125, "1561957126": 14557.6796875}
  }
  
  df = json_normalize(data, record_path=['dps'], meta=['metric',['tags','site'],['tags','peer']])
  print (df)
  </code></pre>
  
  <p>Output :</p>
  
  <pre><code>             0           metric tags:site tags:peer
  0   1561953835  peer.traffic.in     site1     peer1
  1   1561954125  peer.traffic.in     site1     peer1
  2   1561954439  peer.traffic.in     site1     peer1
  3   1561954728  peer.traffic.in     site1     peer1
  4   1561955039  peer.traffic.in     site1     peer1
  5   1561955329  peer.traffic.in     site1     peer1
  6   1561955641  peer.traffic.in     site1     peer1
  7   1561955928  peer.traffic.in     site1     peer1
  8   1561956241  peer.traffic.in     site1     peer1
  9   1561956533  peer.traffic.in     site1     peer1
  10  1561956847  peer.traffic.in     site1     peer1
  11  1561957126  peer.traffic.in     site1     peer1
  </code></pre>
  
  <p>I would expect to see the values to show up in the table from the <code>dps</code> table.</p>