docs: def read_array(self, infile, var_name):
          """Directly return a numpy array for a given variable name"""
          file_handle = self.read_cdf(infile)
          try:
              # return the data array
              return file_handle.variables[var_name][:]
          except KeyError:
              print("Cannot find variable: {0}".format(var_name))
              raise KeyError