framework/data/BaseDataProvider.php
public function prepare($forcePrepare = false)
    {
        if ($forcePrepare || $this->_models === null) {
            $this->_models = $this->prepareModels();
        }
        if ($forcePrepare || $this->_keys === null) {
            $this->_keys = $this->prepareKeys($this->_models);
        }
    }
public function prepare($forcePrepare = false)
    {
        if ($forcePrepare || $this->_models === null) {
            $this->_models = $this->prepareModels();
        }
        if ($forcePrepare || $this->_keys === null) {
            $this->_keys = $this->prepareKeys($this->_models);
        }
    }
Prepares the data models and keys.

This method will prepare the data models and keys that can be retrieved via
[[getModels()]] and [[getKeys()]].

This method will be implicitly called by [[getModels()]] and [[getKeys()]] if it has not been called before.

@param bool $forcePrepare whether to force data preparation even if it has been done before.