Return a cdf handle created by the available cdf library.
        python-netcdf4 and scipy supported (default:scipy)

def read_cdf(self, infile):
        """Return a cdf handle created by the available cdf library.
        python-netcdf4 and scipy supported (default:scipy)"""
        if not self.return_cdf:
            self.load_cdf_module()

        if self.cdf_module == "scipy":
            # making it compatible to older scipy versions
            file_obj = self.cdf.netcdf_file(infile, mode="r")
        elif self.cdf_module == "netcdf4":
            file_obj = self.cdf.Dataset(infile)
        else:
            raise ImportError(
                "Could not import data \
                              from file {0}".format(
                    infile
                )
            )
        return file_obj