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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _validate_alias_name(alias_name):
 """ Check if the alias name is valid. Args: alias_name: The name of the alias to validate. """

    if not alias_name:
        raise CLIError(EMPTY_ALIAS_ERROR)

    if not re.match('^[a-zA-Z]', alias_name):
        raise CLIError(INVALID_STARTING_CHAR_ERROR.format(alias_name[0]))