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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 add_line(self, start, end, color=(0.5, 0.5, 0.5), width=1):
 """ Adds a line. Args: start: Starting coordinates for line. end: Ending coordinates for line. color: Color for text as RGB. Defaults to grey. width: Width of line. Defaults to 1. """

        source = vtk.vtkLineSource()
        source.SetPoint1(start)
        source.SetPoint2(end)

        vertexIDs = vtk.vtkStringArray()
        vertexIDs.SetNumberOfComponents(1)
        vertexIDs.SetName("VertexIDs")
        # Set the vertex labels
        vertexIDs.InsertNextValue("a")
        vertexIDs.InsertNextValue("b")
        source.GetOutput().GetPointData().AddArray(vertexIDs)

        mapper = vtk.vtkPolyDataMapper()
        mapper.SetInputConnection(source.GetOutputPort())
        actor = vtk.vtkActor()
        actor.SetMapper(mapper)
        actor.GetProperty().SetColor(color)
        actor.GetProperty().SetLineWidth(width)
        self.ren.AddActor(actor)