src/SchemaAnalyzer.php
public function getParentRelationship($tableName)
    {
        return $this->fromCache($this->cachePrefix.'_parent_'.$tableName, function () use ($tableName) {
            return $this->getParentRelationshipWithoutCache($tableName);
        });
    }
public function getParentRelationship($tableName)
    {
        return $this->fromCache($this->cachePrefix.'_parent_'.$tableName, function () use ($tableName) {
            return $this->getParentRelationshipWithoutCache($tableName);
        });
    }
If this table is pointing to a parent table (if its primary key is a foreign key pointing on another table),
this function will return the pointed table.
This function will return null if there is no parent table.

@param string $tableName

@return ForeignKeyConstraint|null