fill docstrings on mixins

ormar/models/mixins/relation_mixin.py

@@ -5,6 +5,10 @@ from ormar.fields.foreign_key import ForeignKeyField
 
 
 class RelationMixin:
+    """
+    Used to return relation fields/names etc. from given model
+    """
+
     if TYPE_CHECKING:  # pragma no cover
         from ormar import ModelMeta
 
@@ -14,6 +18,12 @@ class RelationMixin:
 
     @classmethod
     def extract_db_own_fields(cls) -> Set:
+        """
+        Returns only fields that are stored in the own database table, exclude all
+        related fields.
+        :return: set of model fields with relation fields excluded
+        :rtype: Set
+        """
         related_names = cls.extract_related_names()
         self_fields = {
             name for name in cls.Meta.model_fields.keys() if name not in related_names
@@ -22,7 +32,13 @@ class RelationMixin:
 
     @classmethod
     def extract_related_fields(cls) -> List:
+        """
+        Returns List of ormar Fields for all relations declared on a model.
+        List is cached in cls._related_fields for quicker access.
 
+        :return: list of related fields
+        :rtype: List
+        """
         if isinstance(cls._related_fields, List):
             return cls._related_fields
 
@@ -35,7 +51,13 @@ class RelationMixin:
 
     @classmethod
     def extract_related_names(cls) -> Set:
+        """
+        Returns List of fields names for all relations declared on a model.
+        List is cached in cls._related_names for quicker access.
 
+        :return: list of related fields names
+        :rtype: List
+        """
         if isinstance(cls._related_names, Set):
             return cls._related_names
 
@@ -49,6 +71,12 @@ class RelationMixin:
 
     @classmethod
     def _extract_db_related_names(cls) -> Set:
+        """
+        Returns only fields that are stored in the own database table, exclude
+        related fields that are not stored as foreign keys on given model.
+        :return: set of model fields with non fk relation fields excluded
+        :rtype: Set
+        """
         related_names = cls.extract_related_names()
         related_names = {
             name
@@ -59,6 +87,17 @@ class RelationMixin:
 
     @classmethod
     def _exclude_related_names_not_required(cls, nested: bool = False) -> Set:
+        """
+        Returns a set of non mandatory related models field names.
+
+        For a main model (not nested) only nullable related field names are returned,
+        for nested models all related models are returned.
+
+        :param nested: flag setting nested models (child of previous one, not main one)
+        :type nested: bool
+        :return: set of non mandatory related fields
+        :rtype: Set
+        """
         if nested:
             return cls.extract_related_names()
         related_names = cls.extract_related_names()