A named list of position weight matrices or position frequency
matrices matching the motif names in data.
Can be of class PFMatrixList.
motif.names
A named list of motif names. List element names
must match the names given in pwm. If NULL, use the names from the list
of position weight or position frequency matrices. This can be used to set
a alternative common name for the motif. If a PFMatrixList is passed to
pwm, it will pull the motif name from the PFMatrixList.