Python: read unstructured to Numpy array

I can read a .vtu file and get the nodes and data. I would like to add a filter CellCenters so I get the parametric cell centers. I need to setup a filter to do this, but I’m new to VTK in Python and unfamiliar with the correct syntax. Here’s what I have that works to read the VTU files:

def read_vtu(file):
    reader = vtk.vtkXMLUnstructuredGridReader()

    output = reader.GetOutput()

    # coordinates of nodes in the mesh
    nodes_vtk = output.GetPoints().GetData()
    nodes = vtk_to_numpy(nodes_vtk)

    data = vtk_to_numpy(output.GetCellData().GetArray("MyVar"))

    return data, nodes