ENH: add new member function filter to Container class

Summary

Allow Container objects to be filtered using ID, name or Entity.

Focus

We use a function that is already used by ParentList and PropertyList

Test Environment

pipelines

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src/doc/tutorials/complex_data_models.rst

@@ -78,7 +78,7 @@ Examples
 
 
 Finding parents and properties
---------
+------------------------------
 To find a specific parent or property of an Entity, its
 ParentList or PropertyList can be filtered using names, ids, or
 entities. A short example:
@@ -100,7+100,7 @@
    properties = r.properties
 
    # As r only has one property with id 101, this returns a list containing only p1_1
    properties.filter(pid=101)
    # Result: [p1_1]
 
    # Filtering with name="Property 1" returns both p1_1 and p1_2, as they share their name
    properties.filter(name="Property 1")
    # Result: [p1_1, p1_2]
 
    #  If both name and pid are given, matching is based only on pid for all entities that have an id
    properties.filter(pid="102", name="Other Property")
    # Result: [p2_1, p2_2, p2_3]
 
@@ -126,7+126,7 @@
    # Result: [p2_1]
 
 The filter function of ParentList works analogously.
+
+Finding entities in a Container
+-------------------------------
+In the same way as described above, Container can be filtered.
+A short example:
+
+.. code-block:: python3
+
+   import linkahead as db
+
+   # Setup a record with six properties
+   p1 = db.Property(id=101, name="Property 1")
+   p2 = db.Property(name="Property 2")
+   c = db.Container().extend([p1,p2])
+   c.filter(name="Property 1")
+   # Result: [p1]

[Alexander Schlemmer]

Is pid a good name? property_id is probably less confusing.

[Alexander Schlemmer]

Is it a real OR-statement (pid OR name)? Would a property with pid=101 and name="Other Property" match? Otherwise I find the behavior not really intuitive.

[Alexander Schlemmer]

does not seem to be the case, because p3 is not matched. I don't like this behavior, because it does correspond to this logical operation which is quite complex: (property.id == pid OR property.id is None) AND (property.name == name OR property.name is None)

What happens if both attributes are None?

Just came to my mind: Why don't implement .filter using a lambda expression, e.g.:

properties.filter(lambda pid, name: pid==101 and name=="Property 1")

This would be much clearer and render the internal behavior more transparent. Also I think the implementation will become much shorter.