has       RelationshipType = "has"
)

type Relationships struct {
	HasOne    []*Relationship
	BelongsTo []*Relationship
	HasMany   []*Relationship
	Many2Many []*Relationship
	Relations map[string]*Relationship

	EmbeddedRelations map[string]*Relationships
}

type Relationship struct {
	Name                     string
	Type                     RelationshipType
	Field                    *Field

	if err != nil {
		t.Fatalf("failed to parse schema, got error %v", err)
	}

	if len(userSchema.Relationships.Relations) != 1 {
		t.Fatalf("expects 1 relations, but got %v", len(userSchema.Relationships.Relations))
	}

	if createdByRel, ok := userSchema.Relationships.Relations["CreatedBy"]; ok {
		if createdByRel.FieldSchema != userSchema {

from sqlalchemy.orm import relationship

from .database import Base


class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True)
    email = Column(String, unique=True, index=True)
    hashed_password = Column(String)
    is_active = Column(Boolean, default=True)

    items = relationship("Item", back_populates="owner")


class Item(Base):

from sqlalchemy.orm import relationship

from .database import Base


class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True)
    email = Column(String, unique=True, index=True)
    hashed_password = Column(String)
    is_active = Column(Boolean, default=True)

    items = relationship("Item", back_populates="owner")


class Item(Base):

from sqlalchemy.orm import relationship

from .database import Base


class User(Base):
    __tablename__ = "users"

    id = Column(Integer, primary_key=True)
    email = Column(String, unique=True, index=True)
    hashed_password = Column(String)
    is_active = Column(Boolean, default=True)

    items = relationship("Item", back_populates="owner")


class Item(Base):

			for _, join := range db.Statement.Joins {
				if db.Statement.Schema != nil {
					var isRelations bool // is relations or raw sql
					var relations []*schema.Relationship
					relation, ok := db.Statement.Schema.Relationships.Relations[join.Name]
					if ok {
						isRelations = true
						relations = append(relations, relation)
					} else {
						// handle nested join like "Manager.Company"

	return names
}

// preloadEntryPoint enters layer by layer. It will call real preload if it finds the right entry point.
// If the current relationship is embedded or joined, current query will be ignored.
//
//nolint:cyclop
func preloadEntryPoint(db *gorm.DB, joins []string, relationships *schema.Relationships, preloads map[string][]interface{}, associationsConds []interface{}) error {
	preloadMap := parsePreloadMap(db.Statement.Schema, preloads)

                              to.
                            type: string
                          operator:
                            description: operator represents a key's relationship
                              to a set of values. Valid operators are In, NotIn, Exists
                              and DoesNotExist.
                            type: string
                          values:

Also, the best approach was to use already existing standards.

So, before even starting to code **FastAPI**, I spent several months studying the specs for OpenAPI, JSON Schema, OAuth2, etc. Understanding their relationship, overlap, and differences.

## Design

Then I spent some time designing the developer "API" I wanted to have as a user (as a developer using FastAPI).

				if r, ok := rs.Relations[n]; !ok {
					t.Errorf("failed to find relation by name %s", n)
				} else {
					checkSchemaRelation(t, &schema.Schema{
						Relationships: schema.Relationships{
							Relations: map[string]*schema.Relationship{n: rel},
						},
					}, r)
				}
			}
			checkEmbeddedRelations(t, relations.EmbeddedRelations, rs.EmbeddedRelations)
		})
	}
}