Theme_My_Login_Form_Field::get_content()

public function get_content() {
    if ( is_callable( $this->content ) ) {
        $content = call_user_func_array( $this->content, array( $this ) );
    } else {
        $content = $this->content;
    }

    /**
     * Filters the form field content.
     *
     * @param string                    $content The field content.
     * @param Theme_My_Login_Form_Field $field   The field object.
     */
    return apply_filters( 'tml_get_form_field_content', $content, $this );
}

View src/includes/class-theme-my-login-form-field.php, line 346 on GitHub