How to use the sqlparse.sql.TokenList function in sqlparse

def test_tokenlist_first():
    p = sqlparse.parse(' select foo')[0]
    first = p.token_first()
    assert first.value == 'select'
    assert p.token_first(skip_ws=False).value == ' '
    assert sql.TokenList([]).token_first() is None

class IdentifierList(TokenList):
    """A list of :class:`~sqlparse.sql.Identifier`\'s."""

    def get_identifiers(self):
        """Returns the identifiers.

        Whitespaces and punctuations are not included in this generator.
        """
        for token in self.tokens:
            if not (token.is_whitespace() or token.match(T.Punctuation, ',')):
                yield token


class Parenthesis(TokenList):
    """Tokens between parenthesis."""
    M_OPEN = T.Punctuation, '('
    M_CLOSE = T.Punctuation, ')'

    @property
    def _groupable_tokens(self):
        return self.tokens[1:-1]


class SquareBrackets(TokenList):
    """Tokens between square brackets"""
    M_OPEN = T.Punctuation, '['
    M_CLOSE = T.Punctuation, ']'

    @property
    def _groupable_tokens(self):

class Function(TokenList):
    """A function or procedure call."""

    def get_parameters(self):
        """Return a list of parameters."""
        parenthesis = self.tokens[-1]
        for token in parenthesis.tokens:
            if isinstance(token, IdentifierList):
                return token.get_identifiers()
            elif imt(token, i=(Function, Identifier), t=T.Literal):
                return [token, ]
        return []


class Begin(TokenList):
    """A BEGIN/END block."""
    M_OPEN = T.Keyword, 'BEGIN'
    M_CLOSE = T.Keyword, 'END'


class Operation(TokenList):
    """Grouping of operations"""

def extract(token_list):
    tokens = list(TokenList(token_list).flatten())
    for token in tokens:
        if token.is_whitespace():
            token.value = " "
    return TokenList(tokens)

return self.tokens[0]

    @property
    def right(self):
        return self.tokens[-1]


class Comment(TokenList):
    """A comment."""
    __slots__ = ('value', 'ttype', 'tokens')

    def is_multiline(self):
        return self.tokens and self.tokens[0].ttype == T.Comment.Multiline


class Where(TokenList):
    """A WHERE clause."""
    __slots__ = ('value', 'ttype', 'tokens')


class Case(TokenList):
    """A CASE statement with one or more WHEN and possibly an ELSE part."""

    __slots__ = ('value', 'ttype', 'tokens')

    def get_cases(self):
        """Returns a list of 2-tuples (condition, value).

        If an ELSE exists condition is None.
        """
        CONDITION = 1
        VALUE = 2

M_CLOSE = T.Keyword, 'END LOOP'


class Comparison(TokenList):
    """A comparison used for example in WHERE clauses."""

    @property
    def left(self):
        return self.tokens[0]

    @property
    def right(self):
        return self.tokens[-1]


class Comment(TokenList):
    """A comment."""

    def is_multiline(self):
        return self.tokens and self.tokens[0].ttype == T.Comment.Multiline


class Where(TokenList):
    """A WHERE clause."""
    M_OPEN = T.Keyword, 'WHERE'
    M_CLOSE = T.Keyword, ('ORDER', 'GROUP', 'LIMIT', 'UNION', 'EXCEPT',
                          'HAVING', 'RETURNING')


class Case(TokenList):
    """A CASE statement with one or more WHEN and possibly an ELSE part."""
    M_OPEN = T.Keyword, 'CASE'

class IdentifierList(TokenList):
    """A list of :class:`~sqlparse.sql.Identifier`\'s."""

    __slots__ = ('value', 'ttype', 'tokens')

    def get_identifiers(self):
        """Returns the identifiers.

        Whitespaces and punctuations are not included in this generator.
        """
        for x in self.tokens:
            if not x.is_whitespace() and not x.match(T.Punctuation, ','):
                yield x


class Parenthesis(TokenList):
    """Tokens between parenthesis."""
    __slots__ = ('value', 'ttype', 'tokens')

    @property
    def _groupable_tokens(self):
        return self.tokens[1:-1]


class SquareBrackets(TokenList):
    """Tokens between square brackets"""

    __slots__ = ('value', 'ttype', 'tokens')

    @property
    def _groupable_tokens(self):
        return self.tokens[1:-1]

elif imt(token, i=(Function, Identifier), t=T.Literal):
                return [token, ]
        return []


class Begin(TokenList):
    """A BEGIN/END block."""
    M_OPEN = T.Keyword, 'BEGIN'
    M_CLOSE = T.Keyword, 'END'


class Operation(TokenList):
    """Grouping of operations"""


class Values(TokenList):
    """Grouping of values"""


class Command(TokenList):
    """Grouping of CLI commands."""

"""An assignment like 'var := val;'"""


class If(TokenList):
    """An 'if' clause with possible 'else if' or 'else' parts."""
    M_OPEN = T.Keyword, 'IF'
    M_CLOSE = T.Keyword, 'END IF'


class For(TokenList):
    """A 'FOR' loop."""
    M_OPEN = T.Keyword, ('FOR', 'FOREACH')
    M_CLOSE = T.Keyword, 'END LOOP'


class Comparison(TokenList):
    """A comparison used for example in WHERE clauses."""

    @property
    def left(self):
        return self.tokens[0]

    @property
    def right(self):
        return self.tokens[-1]


class Comment(TokenList):
    """A comment."""

    def is_multiline(self):
        return self.tokens and self.tokens[0].ttype == T.Comment.Multiline

class If(TokenList):
    """An 'if' clause with possible 'else if' or 'else' parts."""
    __slots__ = ('value', 'ttype', 'tokens')


class For(TokenList):
    """A 'FOR' loop."""
    __slots__ = ('value', 'ttype', 'tokens')


class Comparison(TokenList):
    """A comparison used for example in WHERE clauses."""
    __slots__ = ('value', 'ttype', 'tokens')


class Comment(TokenList):
    """A comment."""
    __slots__ = ('value', 'ttype', 'tokens')


class Where(TokenList):
    """A WHERE clause."""
    __slots__ = ('value', 'ttype', 'tokens')


class Case(TokenList):
    """A CASE statement with one or more WHEN and possibly an ELSE part."""

    __slots__ = ('value', 'ttype', 'tokens')

    def get_cases(self):
        """Returns a list of 2-tuples (condition, value).