<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def format_var_name(variable, var_list):
 """ Searches var list for variable name, checks other variable name format options. Args: variable (str):
 Variable being loaded var_list (list):
 List of variables in file. Returns: Name of variable in file containing relevant data, and index of variable z-level if multiple variables contained in same array in file. """

        z_index = None
        if variable in var_list:
            var_name = variable
        elif variable.ljust(6, "_") in var_list:
            var_name = variable.ljust(6, "_")
        elif any([variable in v_sub.split("_") for v_sub in var_list]):
            var_name = var_list[[variable in v_sub.split("_") for v_sub in var_list].index(True)]
            z_index = var_name.split("_").index(variable)
        else:
            raise KeyError("{0} not found in {1}".format(variable, var_list))
        return var_name, z_index