def get_lon_variable(nc):
if '<STR_LIT>' in nc.variables:<EOL><INDENT>return '<STR_LIT>'<EOL><DEDENT>longitudes = nc.get_variables_by_attributes(standard_name="<STR_LIT>")<EOL>if longitudes:<EOL><INDENT>return longitudes[<NUM_LIT:0>].name<EOL><DEDENT>return None<EOL>
Returns the variable for longitude

:param netCDF4.Dataset nc: netCDF dataset