```python

q = QueryTool()

# Group filter
# Using the same thing than SQL Alchemy
q.filter_group("group1", "group2") # group1 AND group2
q.filter_group(or_("group1", "group2")) # group1 OR group2
q.filter_group(not_("group1")) # NOT group1
# Is there a need to do group1 AND (group2 OR NOT group3) ?

# Node type filter: support of basic boolean expr ?
q.filter_class(Calculation) # using class or string ?
q.filter_class(not_(Calculation))
q.filter_class(Calculation, ParameterData) # OR statement, AND doesn't make
# sense here

# We either use kwargs to filter, or we implement custom method: filter_owner,
# filter_time, filter_label. Might conflict if we implement querying on other
# part of the DB later on.
q.filter_node(type="..", owner="..") # Owner: using an user id, email, first/last name ?
q.filter_node(label=or_("truc1", "truc2"), owner=or_("user1", "user2"))
# Time
q.filter_node(time=("from", "to"))
q.filter_node(time=or_(("from", "to"), ("from", "to")))
or q.filter_node(time(from=.., to=..))
q.filter_node(or_(time(from=.., to=..), time(from=.., to=..)))

# Attribute filter (same for extra, but filter_extra instead)
q.filter_attr("attr_name", "<=", 0., label=.., on="inputs", prefetch=True) # self explanatory
q.filter_attr("attr_name", "<=", 0., on="parents", label=.., depth=5) # Filter with a max depth

# Prefetching
q.prefetch("attr_name", on="relation") # Relation being input or output, that is
# only one depth more. Still have to think what prefetching could look like with
# more than 1 depth, if we allow more than one depth.

# Placeholder: used in selecting stuff like atoms.*.0, and disallow dots in the *
# placeholder.
q.filter_attr("atoms.*.0", "=", "O")

# Query chaining
# Still have to define what it should be.
q1 = QueryTool()
# .. operations on q1
q2 = QueryTool()
```