src/Schema.php
public function hasMixin($mixinId)
    {
        return isset($this->mixins[$mixinId]) || isset($this->mixinsByCurie[$mixinId]);
    }
public function hasMixin($mixinId)
    {
        return isset($this->mixins[$mixinId]) || isset($this->mixinsByCurie[$mixinId]);
    }
Returns true if the mixin is on this schema.  Id provided can be
qualified to major rev or just the curie.
@see SchemaId::getCurieMajor

@param string $mixinId

@return bool