processing-script.py

from qgis.core import (QgsProcessingParameterFeatureSource,
                       QgsProcessingParameterField,
                       QgsProcessingParameterFileDestination,
                       QgsProcessingUtils,
                       QgsProcessingAlgorithm)


class myScript(QgsProcessingAlgorithm):

    INPUT = 'INPUT'
    OUTPUT = 'OUTPUT'

    def __init__(self):
        super().__init__()


    def group(self):
        return 'My group'

    def name(self):
        return 'my algorithm'
    
    def displayName(self):
        return 'vaffanculo'
        
    def initAlgorithm(self, config=None):
        self.addParameter(QgsProcessingParameterFeatureSource(self.INPUT,
                                                              'Input layer'))