def __read_seq_header(fh, prev_line):
seq_header = "<STR_LIT>"<EOL>if prev_line is not None and not _isSequenceHead(prev_line):<EOL><INDENT>raise FastaFileFormatError("<STR_LIT>" + prev_line)<EOL><DEDENT>if prev_line is None:<EOL><INDENT>while seq_header.strip() == "<STR_LIT>":<EOL><INDENT>seq_header = fh.readline()<EOL><DEDENT><DEDENT>else:<EOL><INDENT>seq_header = prev_line<EOL><DEDENT>return seq_header<EOL>
Given a file handle/stream, read the next fasta header from that stream.

:param fh:         filehandle to read from
:param prev_line:  the previous line read from this filestream