numRequiredSignatures property
The total number of signatures required to make the transaction valid. The signatures must
match the first numRequiredSignatures of Message.accountKeys.
Example:
If Transaction.signatures = ['signature1', 'signature0', 'signature2'],
then numRequiredSignatures must = 3,
and the first 3 public keys in Message.accountKeys will be the Transaction.signatures'
corresponding public keys in the same order ['pk1', 'pk0', 'pk2', ...].
Implementation
final int numRequiredSignatures;