<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def removeModifications(peptide):
 """Removes all modifications from a peptide string and return the plain amino acid sequence. :param peptide: peptide sequence, modifications have to be written in the format "[modificationName]" :param peptide: str :returns: amino acid sequence of ``peptide`` without any modifications """

    while peptide.find('[') != -1:
        peptide = peptide.split('[', 1)[0] + peptide.split(']', 1)[1]
    return peptide