Checks whether a file is Mini-SEED/full SEED or not.

Parameters:filename (str) Mini-SEED/full SEED file to be checked.
Return type:bool
Returns:True if a Mini-SEED file.

This method only reads the first seven bytes of the file and checks whether its a Mini-SEED or full SEED file.

It also is true for fullSEED files because libmseed can read the data part of fullSEED files. If the method finds a fullSEED file it also checks if it has a data part and returns False otherwise.

Thus it cannot be used to validate a Mini-SEED or SEED file.