## FastAPI Experts

The people that help others the most in GitHub Discussions can become [**FastAPI Experts**](./fastapi-people.md#fastapi-experts){.internal-link target=_blank}.

This is normally the best way to contribute to the project.

## External Contributions

External contributions are very welcome and appreciated, including answering questions, submitting PRs, etc. 🙇‍♂️

    return ensureInUnitRange(sumOfProductsOfDeltas / Math.sqrt(productOfSumsOfSquaresOfDeltas));
  }

  /**
   * Returns a linear transformation giving the best fit to the data according to <a
   * href="http://mathworld.wolfram.com/LeastSquaresFitting.html">Ordinary Least Squares linear
   * regression</a> of {@code y} as a function of {@code x}. The count must be greater than one, and

/**
 * Marks all "top-level" types as non-null in a way that is recognized by Kotlin. Note that this
 * unfortunately includes type-variable usages, so we also provide {@link ParametricNullness} to
 * "undo" it as best we can.
 */
@GwtCompatible
@Retention(RUNTIME)
@Target(TYPE)
@TypeQualifierDefault({FIELD, METHOD, PARAMETER})
@Nonnull

/**
 * Marks all "top-level" types as non-null in a way that is recognized by Kotlin. Note that this
 * unfortunately includes type-variable usages, so we also provide {@link ParametricNullness} to
 * "undo" it as best we can.
 */
@GwtCompatible
@Retention(RUNTIME)
@Target(TYPE)
@TypeQualifierDefault({FIELD, METHOD, PARAMETER})
@Nonnull

/**
 * Marks all "top-level" types as non-null in a way that is recognized by Kotlin. Note that this
 * unfortunately includes type-variable usages, so we also provide {@link ParametricNullness} to
 * "undo" it as best we can.
 */
@GwtCompatible
@Retention(RUNTIME)
@Target(TYPE)
@TypeQualifierDefault({FIELD, METHOD, PARAMETER})
@Nonnull

/**
 * Marks all "top-level" types as non-null in a way that is recognized by Kotlin. Note that this
 * unfortunately includes type-variable usages, so we also provide {@link ParametricNullness} to
 * "undo" it as best we can.
 */
@GwtCompatible
@Retention(RUNTIME)
@Target(TYPE)
@TypeQualifierDefault({FIELD, METHOD, PARAMETER})
@Nonnull

/**
 * Marks all "top-level" types as non-null in a way that is recognized by Kotlin. Note that this
 * unfortunately includes type-variable usages, so we also provide {@link ParametricNullness} to
 * "undo" it as best we can.
 */
@GwtCompatible
@Retention(RUNTIME)
@Target(TYPE)
@TypeQualifierDefault({FIELD, METHOD, PARAMETER})
@Nonnull

type GetDBConnector interface {
	GetDBConn() (*sql.DB, error)
}

// Rows rows interface
type Rows interface {
	Columns() ([]string, error)
	ColumnTypes() ([]*sql.ColumnType, error)
	Next() bool
	Scan(dest ...interface{}) error
	Err() error
	Close() error
}

type ErrorTranslator interface {
	Translate(err error) error

/**
 * Marks all "top-level" types as non-null in a way that is recognized by Kotlin. Note that this
 * unfortunately includes type-variable usages, so we also provide {@link ParametricNullness} to
 * "undo" it as best we can.
 */
@GwtCompatible
@Retention(RUNTIME)
@Target(TYPE)
@TypeQualifierDefault({FIELD, METHOD, PARAMETER})
@Nonnull

/**
 * Marks all "top-level" types as non-null in a way that is recognized by Kotlin. Note that this
 * unfortunately includes type-variable usages, so we also provide {@link ParametricNullness} to
 * "undo" it as best we can.
 */
@GwtCompatible
@Retention(RUNTIME)
@Target(TYPE)
@TypeQualifierDefault({FIELD, METHOD, PARAMETER})
@Nonnull