How to use the chameleon.core.types.declaration function in Chameleon

"""

        variables = []
        for var in string.split(','):
            var = var.strip()

            if var in ('repeat',):
                raise ValueError, "Invalid variable name '%s' (reserved)." % var

            if var.startswith('_') and not var.startswith('_tmp'):
                raise ValueError(
                    "Invalid variable name '%s' (starts with an underscore)." % var)

            variables.append(var)

        return types.declaration(variables)

"""

        variables = []
        for var in string.split(','):
            var = var.strip()

            if var in ('repeat',):
                raise ValueError, "Invalid variable name '%s' (reserved)." % var

            if var.startswith('_') and not var.startswith('_tmp'):
                raise ValueError(
                    "Invalid variable name '%s' (starts with an underscore)." % var)

            variables.append(var)

        return types.declaration(variables)

def __init__(self, declaration, expression=None, dictionary=None):
        if not isinstance(declaration, types.declaration):
            declaration = types.declaration((declaration,))

        if len(declaration) == 1:
            variable = declaration[0]
        else:
            variable = u"(%s,)" % ", ".join(declaration)

        if declaration.global_scope and dictionary is not None:
           variable = "%s['%s'] = %s" % (dictionary, variable, variable)

        if expression is not None:
            self.assign = Assign(expression, variable)

        self.declaration = declaration
        self.dictionary = dictionary

def assign(self):
            content = self._content
            if content is not None:
                definition = (
                    types.declaration((self.content_symbol,)),
                    content)
                return types.definitions((definition,))

def __init__(self, declaration, expression=None, dictionary=None):
        if not isinstance(declaration, types.declaration):
            declaration = types.declaration((declaration,))

        if len(declaration) == 1:
            variable = declaration[0]
        else:
            variable = u"(%s,)" % ", ".join(declaration)

        if declaration.global_scope and dictionary is not None:
           variable = "%s['%s'] = %s" % (dictionary, variable, variable)

        if expression is not None:
            self.assign = Assign(expression, variable)

        self.declaration = declaration
        self.dictionary = dictionary