How to use the parso.tree.Leaf function in parso

"""
        Given a (line, column) tuple, returns a :py:class:`Name` or ``None`` if
        there is no name at that position.
        """
        for c in self.children:
            if isinstance(c, Leaf):
                if c.type == 'name' and c.start_pos <= position <= c.end_pos:
                    return c
            else:
                result = c.get_name_of_position(position)
                if result is not None:
                    return result
        return None


class PythonLeaf(PythonMixin, Leaf):
    __slots__ = ()

    def _split_prefix(self):
        return split_prefix(self, self.get_start_pos_of_prefix())

    def get_start_pos_of_prefix(self):
        """
        Basically calls :py:meth:`parso.tree.NodeOrLeaf.get_start_pos_of_prefix`.
        """
        # TODO it is really ugly that we have to override it. Maybe change
        #   indent error leafs somehow? No idea how, though.
        previous_leaf = self.get_previous_leaf()
        if previous_leaf is not None and previous_leaf.type == 'error_leaf' \
                and previous_leaf.token_type in ('INDENT', 'DEDENT', 'ERROR_DEDENT'):
            previous_leaf = previous_leaf.get_previous_leaf()

def get_name_of_position(self, position):
        """
        Given a (line, column) tuple, returns a :py:class:`Name` or ``None`` if
        there is no name at that position.
        """
        for c in self.children:
            if isinstance(c, Leaf):
                if c.type == 'name' and c.start_pos <= position <= c.end_pos:
                    return c
            else:
                result = c.get_name_of_position(position)
                if result is not None:
                    return result
        return None

self.value,
            flags=re.DOTALL
        )
        return match.group(2)[:-len(match.group(1))]


class FStringString(Leaf):
    """
    f-strings contain f-string expressions and normal python strings. These are
    the string parts of f-strings.
    """
    type = 'fstring_string'
    __slots__ = ()


class FStringStart(Leaf):
    """
    f-strings contain f-string expressions and normal python strings. These are
    the string parts of f-strings.
    """
    type = 'fstring_start'
    __slots__ = ()


class FStringEnd(Leaf):
    """
    f-strings contain f-string expressions and normal python strings. These are
    the string parts of f-strings.
    """
    type = 'fstring_end'
    __slots__ = ()

def get_name_of_position(self, position):
        """
        Given a (line, column) tuple, returns a :py:class:`Name` or ``None`` if
        there is no name at that position.
        """
        for c in self.children:
            if isinstance(c, Leaf):
                if c.type == 'name' and c.start_pos <= position <= c.end_pos:
                    return c
            else:
                result = c.get_name_of_position(position)
                if result is not None:
                    return result
        return None

A Parser instance contains state pertaining to the current token
    sequence, and should not be used concurrently by different threads
    to parse separate token sequences.

    See python/tokenize.py for how to get input tokens by a string.

    When a syntax error occurs, error_recovery() is called.
    """

    node_map = {}
    default_node = tree.Node

    leaf_map = {
    }
    default_leaf = tree.Leaf

    def __init__(self, pgen_grammar, start_nonterminal='file_input', error_recovery=False):
        self._pgen_grammar = pgen_grammar
        self._start_nonterminal = start_nonterminal
        self._error_recovery = error_recovery

    def parse(self, tokens):
        first_dfa = self._pgen_grammar.nonterminal_to_dfas[self._start_nonterminal][0]
        self.stack = Stack([StackNode(first_dfa)])

        for token in tokens:
            self._add_token(token)

        while True:
            tos = self.stack[-1]
            if not tos.dfa.is_final:

def get_name_of_position(self, position):
        """
        Given a (line, column) tuple, returns a :py:class:`Name` or ``None`` if
        there is no name at that position.
        """
        for c in self.children:
            if isinstance(c, Leaf):
                if c.type == 'name' and c.start_pos <= position <= c.end_pos:
                    return c
            else:
                result = c.get_name_of_position(position)
                if result is not None:
                    return result
        return None

def __repr__(self):
        return "%s(%s, %r)" % (self.__class__.__name__, self.type, self.children)


class ErrorNode(BaseNode):
    """
    A node that contains valid nodes/leaves that we're follow by a token that
    was invalid. This basically means that the leaf after this node is where
    Python would mark a syntax error.
    """
    __slots__ = ()
    type = 'error_node'


class ErrorLeaf(Leaf):
    """
    A leaf that is either completely invalid in a language (like `$` in Python)
    or is invalid at that position. Like the star in `1 +* 1`.
    """
    __slots__ = ('token_type',)
    type = 'error_leaf'

    def __init__(self, token_type, value, start_pos, prefix=''):
        super(ErrorLeaf, self).__init__(value, start_pos, prefix)
        self.token_type = token_type

    def __repr__(self):
        return "<%s: %s:%s, %s>" % \
            (type(self).__name__, self.token_type, repr(self.value), self.start_pos)

indent = leaf.start_pos[1]

            if previous_leaf is not None:
                stmt = previous_leaf
                while True:
                    stmt = search_ancestor(
                        stmt, 'if_stmt', 'for_stmt', 'while_stmt', 'try_stmt',
                        'error_node',
                    )
                    if stmt is None:
                        break

                    type_ = stmt.type
                    if type_ == 'error_node':
                        first = stmt.children[0]
                        if isinstance(first, Leaf):
                            type_ = first.value + '_stmt'
                    # Compare indents
                    if stmt.start_pos[1] == indent:
                        if type_ == 'if_stmt':
                            allowed_keywords += ['elif', 'else']
                        elif type_ == 'try_stmt':
                            allowed_keywords += ['except', 'finally', 'else']
                        elif type_ == 'for_stmt':
                            allowed_keywords.append('else')

        completion_names = list(self._get_keyword_completion_names(allowed_keywords))

        if token.NAME in allowed_tokens or token.INDENT in allowed_tokens:
            # This means that we actually have to do type inference.

            symbol_names = list(self.stack.get_node_names(grammar._pgen_grammar))

def get_name_of_position(self, position):
        """
        Given a (line, column) tuple, returns a :py:class:`Name` or ``None`` if
        there is no name at that position.
        """
        for c in self.children:
            if isinstance(c, Leaf):
                if c.type == 'name' and c.start_pos <= position <= c.end_pos:
                    return c
            else:
                result = c.get_name_of_position(position)
                if result is not None:
                    return result
        return None