New returns a new Pool struct.

ErrConflict is returned when transaction being added is incompatible with the contents of the memory pool (Sender doesn't have enough GAS to pay for all transactions in the pool).

ErrConflictsAttribute is returned when transaction conflicts with other transactions due to its (or theirs) nonce.

ErrDup is returned when transaction being added is already present in the memory pool.

ErrInsufficientFunds is returned when Sender is not able to pay for transaction being added irrespective of the other contents of the pool.

ErrOOM is returned when transaction just doesn't fit in the memory pool because of its capacity constraints.

Pool stores the unconfirms transactions.

Feer is an interface that abstract the implementation of the fee calculation.