<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _add_dependency(self, key, dependlist, i, isSubroutine, anexec):
 """Determines whether the item in the dependency list is a valid function call by excluding local variables and members."""

        #First determine if the reference is to a derived type variable
        lkey = key.lower()
        if "%" in key:
            #Find the type of the base variable and then perform a tree
            #search at the module level to determine if the final reference
            #is a valid executable
            base = key.split("%")[0]
            ftype = None
            if base in anexec.members and anexec.members[base].is_custom:
                ftype = anexec.members[base].kind
            elif base in anexec.parameters and anexec.parameters[base].is_custom:
                ftype = anexec.parameters[base].kind

            if ftype is not None:
                end = anexec.module.type_search(ftype, key)
                if end is not None and isinstance(end, TypeExecutable):
                    #We have to overwrite the key to include the actual name of the type
                    #that is being referenced instead of the local name of its variable.
                    tname = "{}%{}".format(ftype, '%'.join(key.split('%')[1:]))
                    d = Dependency(tname, dependlist[i + 1], isSubroutine, anexec)
                    anexec.add_dependency(d)
                    
        elif lkey not in ["for", "forall", "do"]:
            #This is a straight forward function/subroutine call, make sure that
            #the symbol is not a local variable or parameter, then add it
            if not lkey in anexec.members and not lkey in anexec.parameters \
               and not lkey in self._intrinsic:                
                #One issue with the logic until now is that some one-line statements
                #like "if (cond) call subroutine" don't trigger the subroutine flag
                #of the dependency.
                if dependlist[i-1] == "call":
                    isSubroutine = True
                d = Dependency(dependlist[i], dependlist[i + 1], isSubroutine, anexec)
                anexec.add_dependency(d)