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.