<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def validate_nodepool_name(namespace):
 """Validates a nodepool name to be at most 12 characters, alphanumeric only."""

    if namespace.nodepool_name != "":
        if len(namespace.nodepool_name) > 12:
            raise CLIError('--nodepool-name can contain atmost 12 characters')
        if not namespace.nodepool_name.isalnum():
            raise CLIError('--nodepool-name should only contain alphanumeric characters')