title: inaccessible due to 'internal' protection level
body: <p>I am implementing the ScrollableGraphView library in my code (<a href="https://github.com/philackm/ScrollableGraphView" rel="noreferrer">https://github.com/philackm/ScrollableGraphView</a>) and experiencing the following problem:</p>
  
  <p>To confirm to ScrollableGraphViewDataSource, when i add</p>
  
  <pre><code>func value(forPlot plot: Plot, atIndex pointIndex: Int) -&gt; Double 
  </code></pre>
  
  <p>to my code, Xcode gives the following error at "plot.identifier" : </p>
  
  <pre><code>'identifier' is inaccessible due to 'internal' protection level. 
  </code></pre>
  
  <p>Can anyone help what is going on?</p>
  
  <pre><code>import UIKit
  
  import ScrollableGraphView
  
  class ViewController: UIViewController, ScrollableGraphViewDataSource {
  
  // Class members and init...
  
  var linePlotData: [Double] = [1, 2, 3, 4, 5]// data for line plot
  var barPlotData: [Double] =  [1, 2, 3, 4, 5]// data for bar plot
  var xAxisLabels: [String] =  ["Jan", "Feb", "Mar", "Apr", "May"]// the labels along the x axis
  
  var numberOfPointsInGraph = 5
  
  override func viewDidLoad() {
      super.viewDidLoad()
  
      let graph = ScrollableGraphView(frame: self.view.frame, dataSource: self)
  
      // Graph Configuration
      // ###################
  
      graph.backgroundColor = UIColor.white
      graph.shouldAnimateOnStartup = true
  
      // Reference Lines
      // ###############
  
      let referenceLines = ReferenceLines()
      referenceLines.positionType = .relative
      referenceLines.relativePositions = [0, 0.5, 0.8, 0.9, 1]
  
      graph.addReferenceLines(referenceLines: referenceLines)
  
      // Adding Plots
      // ############
  
      let linePlot = LinePlot(identifier: "linePlot")
      linePlot.lineWidth = 5
      linePlot.lineColor = UIColor.black
  
      let barPlot = BarPlot(identifier: "barPlot")
      barPlot.barWidth = 20
      barPlot.barLineColor = UIColor.gray
  
      graph.addPlot(plot: linePlot)
      graph.addPlot(plot: barPlot)
  
      self.view.addSubview(graph)
  }
  
  // Implementation for ScrollableGraphViewDataSource protocol
  func value(forPlot plot: Plot, atIndex pointIndex: Int) -&gt; Double {
  
      switch (plot.identifier) {
      case "linePlot":
          return linePlotData[pointIndex]
          break
      case "barPlot":
          return barPlotData[pointIndex]
          break
      }
  }
  
  func label(atIndex pointIndex: Int) -&gt; String {
      return xAxisLabels[pointIndex]
  }
  
  func numberOfPoints() -&gt; Int {
      return numberOfPointsInGraph
  }
  }
  </code></pre>