code: func NewSigCache(maxEntries uint) *SigCache {
  	return &SigCache{
  		validSigs:  make(map[chainhash.Hash]sigCacheEntry, maxEntries),
  		maxEntries: maxEntries,
  	}
  }
docs: // NewSigCache creates and initializes a new instance of SigCache. Its sole
  // parameter 'maxEntries' represents the maximum number of entries allowed to
  // exist in the SigCache at any particular moment. Random entries are evicted
  // to make room for new entries that would cause the number of entries in the
  // cache to exceed the max.